Fix imagefolder dataset url


The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/datasets/pr_6683). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

<details>
<summary>Show benchmarks</summary>

PyArrow==8.0.0

<details>
<summary>Show updated benchmarks!</summary>

### Benchmark: benchmark_array_xd.json

| metric | read_batch_formatted_as_numpy after write_array2d | read_batch_formatted_as_numpy after write_flattened_sequence | read_batch_formatted_as_numpy after write_nested_sequence | read_batch_unformated after write_array2d | read_batch_unformated after write_flattened_sequence | read_batch_unformated after write_nested_sequence | read_col_formatted_as_numpy after write_array2d | read_col_formatted_as_numpy after write_flattened_sequence | read_col_formatted_as_numpy after write_nested_sequence | read_col_unformated after write_array2d | read_col_unformated after write_flattened_sequence | read_col_unformated after write_nested_sequence | read_formatted_as_numpy after write_array2d | read_formatted_as_numpy after write_flattened_sequence | read_formatted_as_numpy after write_nested_sequence | read_unformated after write_array2d | read_unformated after write_flattened_sequence | read_unformated after write_nested_sequence | write_array2d | write_flattened_sequence | write_nested_sequence |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.005501 / 0.011353 (-0.005851) | 0.003907 / 0.011008 (-0.007101) | 0.063524 / 0.038508 (0.025016) | 0.031773 / 0.023109 (0.008664) | 0.244672 / 0.275898 (-0.031226) | 0.293342 / 0.323480 (-0.030138) | 0.004091 / 0.007986 (-0.003895) | 0.002837 / 0.004328 (-0.001491) | 0.049181 / 0.004250 (0.044930) | 0.044515 / 0.037052 (0.007462) | 0.263932 / 0.258489 (0.005443) | 0.288412 / 0.293841 (-0.005429) | 0.028338 / 0.128546 (-0.100208) | 0.010865 / 0.075646 (-0.064781) | 0.207979 / 0.419271 (-0.211293) | 0.036149 / 0.043533 (-0.007384) | 0.250674 / 0.255139 (-0.004465) | 0.263232 / 0.283200 (-0.019968) | 0.017919 / 0.141683 (-0.123763) | 1.127794 / 1.452155 (-0.324360) | 1.172071 / 1.492716 (-0.320645) |

### Benchmark: benchmark_getitem\_100B.json

| metric | get_batch_of\_1024\_random_rows | get_batch_of\_1024\_rows | get_first_row | get_last_row |
|--------|---|---|---|---|
| new / old (diff) | 0.090435 / 0.018006 (0.072429) | 0.300041 / 0.000490 (0.299552) | 0.000217 / 0.000200 (0.000018) | 0.000052 / 0.000054 (-0.000002) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.018986 / 0.037411 (-0.018426) | 0.064872 / 0.014526 (0.050346) | 0.074738 / 0.176557 (-0.101818) | 0.121577 / 0.737135 (-0.615558) | 0.076416 / 0.296338 (-0.219923) |

### Benchmark: benchmark_iterating.json

| metric | read 5000 | read 50000 | read_batch 50000 10 | read_batch 50000 100 | read_batch 50000 1000 | read_formatted numpy 5000 | read_formatted pandas 5000 | read_formatted tensorflow 5000 | read_formatted torch 5000 | read_formatted_batch numpy 5000 10 | read_formatted_batch numpy 5000 1000 | shuffled read 5000 | shuffled read 50000 | shuffled read_batch 50000 10 | shuffled read_batch 50000 100 | shuffled read_batch 50000 1000 | shuffled read_formatted numpy 5000 | shuffled read_formatted_batch numpy 5000 10 | shuffled read_formatted_batch numpy 5000 1000 |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.279471 / 0.215209 (0.064262) | 2.743066 / 2.077655 (0.665411) | 1.429511 / 1.504120 (-0.074609) | 1.315391 / 1.541195 (-0.225804) | 1.371255 / 1.468490 (-0.097235) | 0.570708 / 4.584777 (-4.014069) | 2.373047 / 3.745712 (-1.372666) | 2.813198 / 5.269862 (-2.456663) | 1.768928 / 4.565676 (-2.796749) | 0.066031 / 0.424275 (-0.358244) | 0.005074 / 0.007607 (-0.002533) | 0.333484 / 0.226044 (0.107440) | 3.295002 / 2.268929 (1.026074) | 1.796089 / 55.444624 (-53.648535) | 1.521849 / 6.876477 (-5.354627) | 1.604417 / 2.142072 (-0.537655) | 0.645235 / 4.805227 (-4.159992) | 0.119226 / 6.500664 (-6.381439) | 0.043275 / 0.075469 (-0.032194) |

### Benchmark: benchmark_map_filter.json

| metric | filter | map fast-tokenizer batched | map identity | map identity batched | map no-op batched | map no-op batched numpy | map no-op batched pandas | map no-op batched pytorch | map no-op batched tensorflow |
|--------|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.986350 / 1.841788 (-0.855438) | 11.921886 / 8.074308 (3.847578) | 9.878841 / 10.191392 (-0.312551) | 0.141072 / 0.680424 (-0.539352) | 0.014514 / 0.534201 (-0.519687) | 0.304060 / 0.579283 (-0.275223) | 0.267844 / 0.434364 (-0.166520) | 0.324881 / 0.540337 (-0.215457) | 0.421426 / 1.386936 (-0.965510) |

</details>
PyArrow==latest

<details>
<summary>Show updated benchmarks!</summary>

### Benchmark: benchmark_array_xd.json

| metric | read_batch_formatted_as_numpy after write_array2d | read_batch_formatted_as_numpy after write_flattened_sequence | read_batch_formatted_as_numpy after write_nested_sequence | read_batch_unformated after write_array2d | read_batch_unformated after write_flattened_sequence | read_batch_unformated after write_nested_sequence | read_col_formatted_as_numpy after write_array2d | read_col_formatted_as_numpy after write_flattened_sequence | read_col_formatted_as_numpy after write_nested_sequence | read_col_unformated after write_array2d | read_col_unformated after write_flattened_sequence | read_col_unformated after write_nested_sequence | read_formatted_as_numpy after write_array2d | read_formatted_as_numpy after write_flattened_sequence | read_formatted_as_numpy after write_nested_sequence | read_unformated after write_array2d | read_unformated after write_flattened_sequence | read_unformated after write_nested_sequence | write_array2d | write_flattened_sequence | write_nested_sequence |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.005322 / 0.011353 (-0.006030) | 0.003942 / 0.011008 (-0.007066) | 0.050629 / 0.038508 (0.012121) | 0.031176 / 0.023109 (0.008066) | 0.279627 / 0.275898 (0.003729) | 0.302667 / 0.323480 (-0.020813) | 0.004281 / 0.007986 (-0.003705) | 0.002900 / 0.004328 (-0.001428) | 0.048168 / 0.004250 (0.043918) | 0.046094 / 0.037052 (0.009042) | 0.290714 / 0.258489 (0.032224) | 0.321336 / 0.293841 (0.027496) | 0.047934 / 0.128546 (-0.080612) | 0.010773 / 0.075646 (-0.064873) | 0.059439 / 0.419271 (-0.359832) | 0.033644 / 0.043533 (-0.009889) | 0.273710 / 0.255139 (0.018571) | 0.295144 / 0.283200 (0.011944) | 0.018115 / 0.141683 (-0.123568) | 1.150302 / 1.452155 (-0.301853) | 1.197304 / 1.492716 (-0.295412) |

### Benchmark: benchmark_getitem\_100B.json

| metric | get_batch_of\_1024\_random_rows | get_batch_of\_1024\_rows | get_first_row | get_last_row |
|--------|---|---|---|---|
| new / old (diff) | 0.090262 / 0.018006 (0.072255) | 0.300727 / 0.000490 (0.300238) | 0.000228 / 0.000200 (0.000028) | 0.000055 / 0.000054 (0.000001) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.022706 / 0.037411 (-0.014706) | 0.077420 / 0.014526 (0.062894) | 0.089119 / 0.176557 (-0.087437) | 0.126760 / 0.737135 (-0.610375) | 0.090702 / 0.296338 (-0.205637) |

### Benchmark: benchmark_iterating.json

| metric | read 5000 | read 50000 | read_batch 50000 10 | read_batch 50000 100 | read_batch 50000 1000 | read_formatted numpy 5000 | read_formatted pandas 5000 | read_formatted tensorflow 5000 | read_formatted torch 5000 | read_formatted_batch numpy 5000 10 | read_formatted_batch numpy 5000 1000 | shuffled read 5000 | shuffled read 50000 | shuffled read_batch 50000 10 | shuffled read_batch 50000 100 | shuffled read_batch 50000 1000 | shuffled read_formatted numpy 5000 | shuffled read_formatted_batch numpy 5000 10 | shuffled read_formatted_batch numpy 5000 1000 |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.296558 / 0.215209 (0.081349) | 2.865311 / 2.077655 (0.787656) | 1.587355 / 1.504120 (0.083235) | 1.491660 / 1.541195 (-0.049534) | 1.513604 / 1.468490 (0.045114) | 0.565209 / 4.584777 (-4.019568) | 2.450648 / 3.745712 (-1.295064) | 2.709941 / 5.269862 (-2.559921) | 1.775032 / 4.565676 (-2.790645) | 0.063767 / 0.424275 (-0.360508) | 0.005047 / 0.007607 (-0.002560) | 0.347406 / 0.226044 (0.121361) | 3.416671 / 2.268929 (1.147743) | 1.949653 / 55.444624 (-53.494971) | 1.669885 / 6.876477 (-5.206592) | 1.848125 / 2.142072 (-0.293947) | 0.648179 / 4.805227 (-4.157048) | 0.116374 / 6.500664 (-6.384290) | 0.041816 / 0.075469 (-0.033653) |

### Benchmark: benchmark_map_filter.json

| metric | filter | map fast-tokenizer batched | map identity | map identity batched | map no-op batched | map no-op batched numpy | map no-op batched pandas | map no-op batched pytorch | map no-op batched tensorflow |
|--------|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 1.007009 / 1.841788 (-0.834779) | 12.749964 / 8.074308 (4.675656) | 10.765890 / 10.191392 (0.574498) | 0.141743 / 0.680424 (-0.538681) | 0.016077 / 0.534201 (-0.518124) | 0.293275 / 0.579283 (-0.286008) | 0.277064 / 0.434364 (-0.157300) | 0.327039 / 0.540337 (-0.213299) | 0.421784 / 1.386936 (-0.965152) |

</details>
</details>

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