do not try to download from HF GCS for generator

attempt to fix https://github.com/huggingface/datasets/issues/6371

Comments:
_The documentation is not available anymore as the PR was closed or merged._

<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) | 0.007617 / 0.011353 (-0.003735) | 0.005371 / 0.011008 (-0.005638) | 0.092110 / 0.038508 (0.053602) | 0.070654 / 0.023109 (0.047544) | 0.362501 / 0.275898 (0.086603) | 0.412835 / 0.323480 (0.089355) | 0.006752 / 0.007986 (-0.001234) | 0.003752 / 0.004328 (-0.000576) | 0.075644 / 0.004250 (0.071394) | 0.055666 / 0.037052 (0.018614) | 0.355906 / 0.258489 (0.097417) | 0.405078 / 0.293841 (0.111237) | 0.045767 / 0.128546 (-0.082779) | 0.013778 / 0.075646 (-0.061868) | 0.324696 / 0.419271 (-0.094575) | 0.062200 / 0.043533 (0.018667) | 0.359571 / 0.255139 (0.104432) | 0.387274 / 0.283200 (0.104075) | 0.035323 / 0.141683 (-0.106360) | 1.586294 / 1.452155 (0.134139) | 1.707564 / 1.492716 (0.214847) |

### 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) | 0.303940 / 0.018006 (0.285934) | 0.583349 / 0.000490 (0.582859) | 0.014845 / 0.000200 (0.014645) | 0.000698 / 0.000054 (0.000643) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.028994 / 0.037411 (-0.008417) | 0.085555 / 0.014526 (0.071029) | 0.097856 / 0.176557 (-0.078701) | 0.161480 / 0.737135 (-0.575655) | 0.098573 / 0.296338 (-0.197766) |

### 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) | 0.591294 / 0.215209 (0.376085) | 5.751350 / 2.077655 (3.673695) | 2.241620 / 1.504120 (0.737500) | 1.991083 / 1.541195 (0.449888) | 2.006711 / 1.468490 (0.538221) | 0.832339 / 4.584777 (-3.752438) | 5.213808 / 3.745712 (1.468095) | 4.650355 / 5.269862 (-0.619506) | 2.860494 / 4.565676 (-1.705182) | 0.093090 / 0.424275 (-0.331185) | 0.009740 / 0.007607 (0.002133) | 0.693509 / 0.226044 (0.467464) | 6.828735 / 2.268929 (4.559807) | 2.967763 / 55.444624 (-52.476862) | 2.311461 / 6.876477 (-4.565016) | 2.400051 / 2.142072 (0.257979) | 0.914753 / 4.805227 (-3.890474) | 0.202804 / 6.500664 (-6.297860) | 0.076905 / 0.075469 (0.001436) |

### 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) | 1.576424 / 1.841788 (-0.265363) | 22.963472 / 8.074308 (14.889164) | 19.948105 / 10.191392 (9.756713) | 0.228982 / 0.680424 (-0.451442) | 0.029038 / 0.534201 (-0.505163) | 0.477715 / 0.579283 (-0.101568) | 0.554924 / 0.434364 (0.120560) | 0.532118 / 0.540337 (-0.008219) | 0.775096 / 1.386936 (-0.611840) |

</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) | 0.009127 / 0.011353 (-0.002226) | 0.004978 / 0.011008 (-0.006030) | 0.084166 / 0.038508 (0.045658) | 0.083391 / 0.023109 (0.060282) | 0.420760 / 0.275898 (0.144862) | 0.459072 / 0.323480 (0.135592) | 0.007102 / 0.007986 (-0.000883) | 0.004175 / 0.004328 (-0.000154) | 0.082922 / 0.004250 (0.078672) | 0.059010 / 0.037052 (0.021957) | 0.416959 / 0.258489 (0.158470) | 0.472220 / 0.293841 (0.178379) | 0.049999 / 0.128546 (-0.078547) | 0.014126 / 0.075646 (-0.061520) | 0.096894 / 0.419271 (-0.322378) | 0.057920 / 0.043533 (0.014387) | 0.405779 / 0.255139 (0.150640) | 0.464286 / 0.283200 (0.181087) | 0.034957 / 0.141683 (-0.106726) | 1.637921 / 1.452155 (0.185767) | 1.768231 / 1.492716 (0.275515) |

### 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) | 0.354875 / 0.018006 (0.336868) | 0.554667 / 0.000490 (0.554177) | 0.074127 / 0.000200 (0.073927) | 0.000411 / 0.000054 (0.000357) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.027681 / 0.037411 (-0.009730) | 0.087746 / 0.014526 (0.073220) | 0.093714 / 0.176557 (-0.082843) | 0.145380 / 0.737135 (-0.591755) | 0.095686 / 0.296338 (-0.200652) |

### 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) | 0.522079 / 0.215209 (0.306870) | 5.197366 / 2.077655 (3.119711) | 2.300744 / 1.504120 (0.796624) | 2.056846 / 1.541195 (0.515652) | 2.009897 / 1.468490 (0.541407) | 0.813025 / 4.584777 (-3.771751) | 5.177732 / 3.745712 (1.432020) | 4.076749 / 5.269862 (-1.193112) | 2.545588 / 4.565676 (-2.020088) | 0.083507 / 0.424275 (-0.340769) | 0.007011 / 0.007607 (-0.000596) | 0.598820 / 0.226044 (0.372776) | 6.203730 / 2.268929 (3.934801) | 2.945385 / 55.444624 (-52.499239) | 2.304849 / 6.876477 (-4.571628) | 2.599035 / 2.142072 (0.456962) | 1.002721 / 4.805227 (-3.802506) | 0.191781 / 6.500664 (-6.308883) | 0.064178 / 0.075469 (-0.011292) |

### 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) | 1.549560 / 1.841788 (-0.292228) | 22.395727 / 8.074308 (14.321418) | 20.537895 / 10.191392 (10.346503) | 0.246542 / 0.680424 (-0.433882) | 0.031673 / 0.534201 (-0.502528) | 0.442490 / 0.579283 (-0.136793) | 0.589838 / 0.434364 (0.155474) | 0.535201 / 0.540337 (-0.005136) | 0.733660 / 1.386936 (-0.653276) |

</details>
</details>

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