Reintroduce clean_text on BertTokenizer call which was removed by mistake in #4723
Author: mfuntowicz
Pull request: yes

Signed-off-by: Morgan Funtowicz <funtowiczmo@gmail.com>

closes #7665 

Comments:
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/5749?src=pr&el=h1) Report
> Merging [#5749](https://codecov.io/gh/huggingface/transformers/pull/5749?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/5668fdb09e1bcd888930c1ff242bf200649da39c?el=desc) will **increase** coverage by `2.02%`.
> The diff coverage is `100.00%`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/5749/graphs/tree.svg?width=650&height=150&src=pr&token=9qOlN6Hb1c)](https://codecov.io/gh/huggingface/transformers/pull/5749?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master    #5749      +/-   ##
==========================================
+ Coverage   75.33%   77.36%   +2.02%     
==========================================
  Files         195      146      -49     
  Lines       39826    26048   -13778     
==========================================
- Hits        30003    20151    -9852     
+ Misses       9823     5897    -3926     
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/5749?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [src/transformers/tokenization\_bert.py](https://codecov.io/gh/huggingface/transformers/pull/5749/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy90b2tlbml6YXRpb25fYmVydC5weQ==) | `95.00% <100.00%> (+2.96%)` | :arrow_up: |
| [src/transformers/commands/env.py](https://codecov.io/gh/huggingface/transformers/pull/5749/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9jb21tYW5kcy9lbnYucHk=) | `0.00% <0.00%> (-100.00%)` | :arrow_down: |
| [src/transformers/commands/\_\_init\_\_.py](https://codecov.io/gh/huggingface/transformers/pull/5749/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9jb21tYW5kcy9fX2luaXRfXy5weQ==) | `0.00% <0.00%> (-100.00%)` | :arrow_down: |
| [src/transformers/commands/transformers\_cli.py](https://codecov.io/gh/huggingface/transformers/pull/5749/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9jb21tYW5kcy90cmFuc2Zvcm1lcnNfY2xpLnB5) | `0.00% <0.00%> (-87.50%)` | :arrow_down: |
| [src/transformers/modeling\_tf\_mobilebert.py](https://codecov.io/gh/huggingface/transformers/pull/5749/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ190Zl9tb2JpbGViZXJ0LnB5) | `23.38% <0.00%> (-73.56%)` | :arrow_down: |
| [src/transformers/commands/download.py](https://codecov.io/gh/huggingface/transformers/pull/5749/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9jb21tYW5kcy9kb3dubG9hZC5weQ==) | `0.00% <0.00%> (-65.00%)` | :arrow_down: |
| [src/transformers/modeling\_tf\_flaubert.py](https://codecov.io/gh/huggingface/transformers/pull/5749/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ190Zl9mbGF1YmVydC5weQ==) | `25.82% <0.00%> (-63.85%)` | :arrow_down: |
| [src/transformers/commands/serving.py](https://codecov.io/gh/huggingface/transformers/pull/5749/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9jb21tYW5kcy9zZXJ2aW5nLnB5) | `0.00% <0.00%> (-55.89%)` | :arrow_down: |
| [src/transformers/commands/run.py](https://codecov.io/gh/huggingface/transformers/pull/5749/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9jb21tYW5kcy9ydW4ucHk=) | `0.00% <0.00%> (-53.34%)` | :arrow_down: |
| [src/transformers/tokenization\_camembert.py](https://codecov.io/gh/huggingface/transformers/pull/5749/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy90b2tlbml6YXRpb25fY2FtZW1iZXJ0LnB5) | `37.03% <0.00%> (-53.13%)` | :arrow_down: |
| ... and [185 more](https://codecov.io/gh/huggingface/transformers/pull/5749/diff?src=pr&el=tree-more) | |

------

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> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/huggingface/transformers/pull/5749?src=pr&el=footer). Last update [5668fdb...25ff60c](https://codecov.io/gh/huggingface/transformers/pull/5749?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).


Do we have unit tests for that `clean_text` functionality 🤔

@stefan-it I'll add one, had to switch to something else in-between 

Do you mind making the code quality and the tests pass before we merge?

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.