Add the ability to skip runtime version check
# 🚀 Feature request

Add the ability to skip version check / raise a warning instead of an error if the checks failed.

## Motivation

Currently, Transformers perform a runtime libraries version check and raise an error if some of the requirements has a version that is different from the specified.

While version check is a reasonable thing to do, an error seems like an overkill. As [I mentioned](https://github.com/huggingface/transformers/pull/8073#issuecomment-765632175) in #8073, this, for example, prevents from using the latest version of Tokenizers without modifying the source code.

## Your contribution

I suggest creating an environment variable (e.g. `TRANSFORMERS_VERSION_CHECK_STRICT`) that would control the reaction to a version mismatch. If it is set to `true`, the current behavior remains. If `false`, we log a warning instead of raising an error. Personally, I think that having this variable `false` by default will make it easier for the users to work in such cases.

What's your opinion in that? Probably we can find an even better solution together.
If anyone else comes here, until this is fixed you can find the version in `transformers/dependency_versions_check.py` - e.g. change `"tokenizers": "tokenizers==0.9.4"` to `"tokenizers": "tokenizers>=0.9.4"`<|||||>This issue has been automatically marked as stale and been closed because it has not had recent activity. Thank you for your contributions.

If you think this still needs to be addressed please comment on this thread.