Fix incomplete docstring for `BuilderConfig`

Fixes #5820
Also fixed a couple of typos I spotted

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) | 0.007658 / 0.011353 (-0.003695) | 0.005497 / 0.011008 (-0.005511) | 0.097142 / 0.038508 (0.058633) | 0.034602 / 0.023109 (0.011493) | 0.304191 / 0.275898 (0.028293) | 0.329103 / 0.323480 (0.005624) | 0.005936 / 0.007986 (-0.002049) | 0.004324 / 0.004328 (-0.000004) | 0.073387 / 0.004250 (0.069137) | 0.049657 / 0.037052 (0.012604) | 0.301352 / 0.258489 (0.042863) | 0.343095 / 0.293841 (0.049254) | 0.036767 / 0.128546 (-0.091779) | 0.012438 / 0.075646 (-0.063208) | 0.333804 / 0.419271 (-0.085468) | 0.064557 / 0.043533 (0.021024) | 0.302397 / 0.255139 (0.047258) | 0.319739 / 0.283200 (0.036540) | 0.119264 / 0.141683 (-0.022418) | 1.465309 / 1.452155 (0.013155) | 1.578194 / 1.492716 (0.085478) |

### 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) | 0.256552 / 0.018006 (0.238545) | 0.555344 / 0.000490 (0.554854) | 0.004845 / 0.000200 (0.004645) | 0.000082 / 0.000054 (0.000027) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.027215 / 0.037411 (-0.010197) | 0.107071 / 0.014526 (0.092545) | 0.116343 / 0.176557 (-0.060213) | 0.172646 / 0.737135 (-0.564490) | 0.123366 / 0.296338 (-0.172973) |

### 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) | 0.411421 / 0.215209 (0.196212) | 4.126028 / 2.077655 (2.048373) | 1.975826 / 1.504120 (0.471706) | 1.784404 / 1.541195 (0.243210) | 1.848697 / 1.468490 (0.380207) | 0.686400 / 4.584777 (-3.898377) | 3.677649 / 3.745712 (-0.068063) | 2.077787 / 5.269862 (-3.192075) | 1.310912 / 4.565676 (-3.254764) | 0.083980 / 0.424275 (-0.340295) | 0.012183 / 0.007607 (0.004575) | 0.506969 / 0.226044 (0.280924) | 5.094730 / 2.268929 (2.825802) | 2.419790 / 55.444624 (-53.024834) | 2.106592 / 6.876477 (-4.769884) | 2.244309 / 2.142072 (0.102237) | 0.814312 / 4.805227 (-3.990915) | 0.167872 / 6.500664 (-6.332792) | 0.065339 / 0.075469 (-0.010130) |

### 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) | 1.193314 / 1.841788 (-0.648474) | 14.980621 / 8.074308 (6.906313) | 14.352452 / 10.191392 (4.161060) | 0.164531 / 0.680424 (-0.515893) | 0.017432 / 0.534201 (-0.516769) | 0.422193 / 0.579283 (-0.157090) | 0.410047 / 0.434364 (-0.024317) | 0.497011 / 0.540337 (-0.043326) | 0.581395 / 1.386936 (-0.805541) |

</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) | 0.007214 / 0.011353 (-0.004139) | 0.005449 / 0.011008 (-0.005559) | 0.074320 / 0.038508 (0.035812) | 0.034261 / 0.023109 (0.011152) | 0.378265 / 0.275898 (0.102367) | 0.414419 / 0.323480 (0.090939) | 0.005804 / 0.007986 (-0.002182) | 0.004205 / 0.004328 (-0.000124) | 0.073266 / 0.004250 (0.069015) | 0.050444 / 0.037052 (0.013392) | 0.372999 / 0.258489 (0.114510) | 0.436032 / 0.293841 (0.142191) | 0.035432 / 0.128546 (-0.093114) | 0.012581 / 0.075646 (-0.063065) | 0.085777 / 0.419271 (-0.333495) | 0.046902 / 0.043533 (0.003369) | 0.378732 / 0.255139 (0.123593) | 0.401746 / 0.283200 (0.118547) | 0.113398 / 0.141683 (-0.028285) | 1.463851 / 1.452155 (0.011696) | 1.566387 / 1.492716 (0.073670) |

### 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) | 0.261246 / 0.018006 (0.243240) | 0.546730 / 0.000490 (0.546241) | 0.005245 / 0.000200 (0.005045) | 0.000103 / 0.000054 (0.000048) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.029441 / 0.037411 (-0.007970) | 0.111834 / 0.014526 (0.097308) | 0.122411 / 0.176557 (-0.054145) | 0.171288 / 0.737135 (-0.565847) | 0.130338 / 0.296338 (-0.166001) |

### 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) | 0.433405 / 0.215209 (0.218196) | 4.315790 / 2.077655 (2.238135) | 2.121934 / 1.504120 (0.617814) | 1.924123 / 1.541195 (0.382928) | 2.029077 / 1.468490 (0.560587) | 0.710245 / 4.584777 (-3.874532) | 3.844393 / 3.745712 (0.098681) | 3.576580 / 5.269862 (-1.693281) | 1.930985 / 4.565676 (-2.634691) | 0.092186 / 0.424275 (-0.332090) | 0.012307 / 0.007607 (0.004700) | 0.533722 / 0.226044 (0.307677) | 5.324447 / 2.268929 (3.055519) | 2.615451 / 55.444624 (-52.829174) | 2.282310 / 6.876477 (-4.594167) | 2.319847 / 2.142072 (0.177774) | 0.849364 / 4.805227 (-3.955864) | 0.172722 / 6.500664 (-6.327942) | 0.064721 / 0.075469 (-0.010748) |

### 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) | 1.289942 / 1.841788 (-0.551846) | 15.875062 / 8.074308 (7.800754) | 14.784682 / 10.191392 (4.593290) | 0.144432 / 0.680424 (-0.535991) | 0.017703 / 0.534201 (-0.516498) | 0.424357 / 0.579283 (-0.154926) | 0.419078 / 0.434364 (-0.015286) | 0.489331 / 0.540337 (-0.051006) | 0.585284 / 1.386936 (-0.801652) |

</details>
</details>

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