TF Flaubert w/ pre-norm
#5614 fixed TF Flaubert without pre-norm, but didn't fix it with the pre-norm.

Fixes #6084

# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/6841?src=pr&el=h1) Report
> Merging [#6841](https://codecov.io/gh/huggingface/transformers/pull/6841?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/05c3214153d30245928279724ce2a9b701ec8aab?el=desc) will **decrease** coverage by `0.10%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/6841/graphs/tree.svg?width=650&height=150&src=pr&token=9qOlN6Hb1c)](https://codecov.io/gh/huggingface/transformers/pull/6841?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master    #6841      +/-   ##
==========================================
- Coverage   80.27%   80.16%   -0.11%     
==========================================
  Files         157      157              
  Lines       28586    28586              
==========================================
- Hits        22946    22916      -30     
- Misses       5640     5670      +30     
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/6841?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [src/transformers/modeling\_tf\_flaubert.py](https://codecov.io/gh/huggingface/transformers/pull/6841/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ190Zl9mbGF1YmVydC5weQ==) | `88.34% <ø> (ø)` | |
| [src/transformers/tokenization\_ctrl.py](https://codecov.io/gh/huggingface/transformers/pull/6841/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy90b2tlbml6YXRpb25fY3RybC5weQ==) | `78.64% <0.00%> (-17.48%)` | :arrow_down: |
| [src/transformers/tokenization\_xlm\_roberta.py](https://codecov.io/gh/huggingface/transformers/pull/6841/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy90b2tlbml6YXRpb25feGxtX3JvYmVydGEucHk=) | `84.52% <0.00%> (-10.72%)` | :arrow_down: |
| [src/transformers/generation\_tf\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/6841/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9nZW5lcmF0aW9uX3RmX3V0aWxzLnB5) | `85.21% <0.00%> (-1.01%)` | :arrow_down: |
| [src/transformers/file\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/6841/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9maWxlX3V0aWxzLnB5) | `82.66% <0.00%> (+0.25%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/huggingface/transformers/pull/6841?src=pr&el=continue).
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> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/huggingface/transformers/pull/6841?src=pr&el=footer). Last update [05c3214...f863f8e](https://codecov.io/gh/huggingface/transformers/pull/6841?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
