Fix typograpical errors
Fixed few typos.
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/2438?src=pr&el=h1) Report
> Merging [#2438](https://codecov.io/gh/huggingface/transformers/pull/2438?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/fb2ab869c6894ea05df97a1372ac9e016ec9c662?src=pr&el=desc) will **decrease** coverage by `0.17%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/2438/graphs/tree.svg?width=650&token=9qOlN6Hb1c&height=150&src=pr)](https://codecov.io/gh/huggingface/transformers/pull/2438?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master    #2438      +/-   ##
==========================================
- Coverage   73.24%   73.06%   -0.18%     
==========================================
  Files          87       87              
  Lines       15001    15001              
==========================================
- Hits        10988    10961      -27     
- Misses       4013     4040      +27
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/2438?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [src/transformers/tokenization\_xlm.py](https://codecov.io/gh/huggingface/transformers/pull/2438/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy90b2tlbml6YXRpb25feGxtLnB5) | `83.26% <100%> (ø)` | :arrow_up: |
| [src/transformers/modeling\_tf\_auto.py](https://codecov.io/gh/huggingface/transformers/pull/2438/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ190Zl9hdXRvLnB5) | `25% <0%> (-7.15%)` | :arrow_down: |
| [src/transformers/pipelines.py](https://codecov.io/gh/huggingface/transformers/pull/2438/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9waXBlbGluZXMucHk=) | `66.37% <0%> (-2.3%)` | :arrow_down: |
| [src/transformers/modeling\_tf\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/2438/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ190Zl91dGlscy5weQ==) | `91.53% <0%> (-1.59%)` | :arrow_down: |
| [src/transformers/tokenization\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/2438/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy90b2tlbml6YXRpb25fdXRpbHMucHk=) | `87.19% <0%> (-0.65%)` | :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/2438?src=pr&el=footer). Last update [fb2ab86...58ca488](https://codecov.io/gh/huggingface/transformers/pull/2438?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
<|||||>Great, thanks @gentaiscool !