Fix token_type_ids for XLM-R
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/2653?src=pr&el=h1) Report
> Merging [#2653](https://codecov.io/gh/huggingface/transformers/pull/2653?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/babd41e7fa07bdd764f8fe91c33469046ab7dbd1?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `0%`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/2653/graphs/tree.svg?width=650&token=9qOlN6Hb1c&height=150&src=pr)](https://codecov.io/gh/huggingface/transformers/pull/2653?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master    #2653   +/-   ##
=======================================
  Coverage   74.58%   74.58%           
=======================================
  Files          87       87           
  Lines       14892    14892           
=======================================
  Hits        11107    11107           
  Misses       3785     3785
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/2653?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [src/transformers/tokenization\_xlm\_roberta.py](https://codecov.io/gh/huggingface/transformers/pull/2653/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy90b2tlbml6YXRpb25feGxtX3JvYmVydGEucHk=) | `32.91% <0%> (ø)` | :arrow_up: |

------

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