Require `tokenizers>=0.11.1`
Author: aphedges
Pull request: yes

# What does this PR do?

I discovered this bug by running on `master` (specifically <https://github.com/huggingface/transformers/commit/515ed3ad2a11a6b0cd9800b2ad4d3b313fdaea8c>). When running the following code, I get the error `Ignored unknown kwarg option direction`:

```python
from transformers import AutoTokenizer
tokenizer = AutoTokenizer.from_pretrained("t5-base")
tokenizer("", truncation="longest_first")
```

This isn't a breaking error (the argument is ignored and training proceeds as normal), but given that I got the error message over 60,000 times in my log file that is 1,000 lines long with this message removed, it's very annoying to work with.

I did some digging, and it was caused when `direction` was added as an input parameter to `tokenizers.Tokenizer.enable_truncation()` in `src/transformers/tokenization_utils_fast.py` as part of <https://github.com/huggingface/transformers/commit/d33dc7966a8c7f04bbca7ae0ced75cbf26c38d9e>. However, the argument was just added to `tokenizers` in <https://github.com/huggingface/tokenizers/commit/152880ab3e5281003bdeee7d1406149e2af97951>, which was first released in `tokenizers==0.11.0`.

If support for `tokenizers>=0.10.1,<0.11` is still desired, I can create a different fix that modifies the code added in <https://github.com/huggingface/transformers/commit/08cb5718ec206bcf34fcd85a03e3e7cbfab8a9e6> to ensure unsupported arguments are filtered out. The code currently handles parameters that `tokenizers` uses but `transformers` does not. I would need to add code that also supports the opposite.

## Before submitting
- [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
- [x] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md#start-contributing-pull-requests), Pull Request section?
- [ ] Was this discussed/approved via a Github issue or the [forum](https://discuss.huggingface.co/)? Please add a link to it if that's the case.
- [ ] Did you make sure to update the documentation with your changes? Here are the [documentation guidelines](https://github.com/huggingface/transformers/tree/master/docs), and [here are tips on formatting docstrings](https://github.com/huggingface/transformers/tree/master/docs#writing-source-documentation).
- [ ] Did you write any new necessary tests?

## Who can review?

tokenizers: @n1t0, @LysandreJik

Comments:
_The documentation is not available anymore as the PR was closed or merged._

@LysandreJik, should the reviewer list in [`.github/PULL_REQUEST_TEMPLATE.md`](https://github.com/huggingface/transformers/blob/38a10c6b52242b1244b510358820603f8a2be3d9/.github/PULL_REQUEST_TEMPLATE.md) be updated with the list in [`.github/ISSUE_TEMPLATE/bug-report.md`](https://github.com/huggingface/transformers/blob/42d57549b82014834706ca86515eb6cc6431b3cb/.github/ISSUE_TEMPLATE/bug-report.md)? I can see the latter has been updated substantially since the former was last modified.

Hey @aphedges, yes indeed! You're correct.

Re-pinging @SaulLu for review. (I know PR review requests can get missed easily. I completely understand.)