Update 01-training-tokenizers.ipynb (typo issue)
I found there are two grammar errors or typo issues in the explanation of the encoding properties.

The original sentences:
- **If your was** made of multiple \"parts\" such as (question, context), then this would be a vector with for each token the segment it belongs to
- **If your has** been truncated into multiple subparts because of a length limit (for BERT for example the sequence length is limited to 512), this will contain all the remaining overflowing parts.

I think "**input**" should be inserted after the phrase "If your".
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/3343?src=pr&el=h1) Report
> Merging [#3343](https://codecov.io/gh/huggingface/transformers/pull/3343?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/f6d813aaaa96cc43fcf55f255b9439ebc22a31a0&el=desc) will **decrease** coverage by `0.08%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/3343/graphs/tree.svg?width=650&height=150&src=pr&token=9qOlN6Hb1c)](https://codecov.io/gh/huggingface/transformers/pull/3343?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master    #3343      +/-   ##
==========================================
- Coverage   77.63%   77.54%   -0.09%     
==========================================
  Files         100      100              
  Lines       16943    16943              
==========================================
- Hits        13154    13139      -15     
- Misses       3789     3804      +15     
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/3343?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [src/transformers/modeling\_tf\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/3343/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ190Zl91dGlscy5weQ==) | `85.68% <0.00%> (-2.69%)` | :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/3343?src=pr&el=footer). Last update [f6d813a...9ecfde1](https://codecov.io/gh/huggingface/transformers/pull/3343?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
<|||||>Thanks!