fix(mlflow): check mlflow version to use the synchronous flag
Author: cchen-dialpad
Pull request: yes

# What does this PR do?

The mlflow integration of `transformers-v4.38.0` will break if the user is using an older mlflow version (< 2.8.0). This PR adds a check on mlflow's version so that it won't break if the user is using an older mlflow version.

Code change in this PR: https://github.com/huggingface/transformers/pull/28779 makes use of the `synchronous` flag for mlflow.log_metrics(), which was introduced only for mlflow version >= 2.8.0. See https://github.com/mlflow/mlflow/pull/9705 and https://github.com/mlflow/mlflow/releases/tag/v2.8.0.


## Before submitting
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      Pull Request section?
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- [ ] Did you write any new necessary tests?


## Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.
@ArthurZucker
@codiceSpaghetti

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Comments:
Let's make sure cis are green!

> Let's make sure cis are green!

Fixed the code quality issue.

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_29195). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.