Remove comma that turns int into tuple
cf @stefan-it's error on Slack
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/4208?src=pr&el=h1) Report
> Merging [#4208](https://codecov.io/gh/huggingface/transformers/pull/4208?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/cafa6a9e29f3e99c67a1028f8ca779d439bc0689&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/4208/graphs/tree.svg?width=650&height=150&src=pr&token=9qOlN6Hb1c)](https://codecov.io/gh/huggingface/transformers/pull/4208?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master    #4208      +/-   ##
==========================================
- Coverage   78.32%   78.31%   -0.02%     
==========================================
  Files         120      120              
  Lines       19854    19854              
==========================================
- Hits        15551    15548       -3     
- Misses       4303     4306       +3     
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/4208?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [src/transformers/trainer.py](https://codecov.io/gh/huggingface/transformers/pull/4208/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy90cmFpbmVyLnB5) | `39.88% <ø> (-0.30%)` | :arrow_down: |
| [src/transformers/file\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/4208/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9maWxlX3V0aWxzLnB5) | `73.96% <0.00%> (-0.42%)` | :arrow_down: |
| [src/transformers/modeling\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/4208/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ191dGlscy5weQ==) | `90.96% <0.00%> (-0.13%)` | :arrow_down: |

------

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> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/huggingface/transformers/pull/4208?src=pr&el=footer). Last update [cafa6a9...bfbed71](https://codecov.io/gh/huggingface/transformers/pull/4208?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
<|||||>Superseded and fixed by #4213 