fix: get mlflow version from mlflow-skinny
Author: clumsy
Pull request: yes

# What does this PR do?

`mlflow` module can be provided by either [mlflow](https://pypi.org/project/mlflow/) or [mlflow-skinny](https://pypi.org/project/mlflow-skinny/) packages. The latter is a more lightweight option.

After a [recent change](https://github.com/huggingface/transformers/pull/29195) the usages of `mlflow-skinny` are broken for `transformers` see [this discussion](https://github.com/huggingface/transformers/pull/29195/files#r1541386713):
```
if packaging.version.parse(importlib.metadata.version("mlflow")) >= packaging.version.parse("2.8.0"):
  File "/opt/conda/lib/python3.9/importlib/metadata.py", line 569, in version
return distribution(distribution_name).version
  File "/opt/conda/lib/python3.9/importlib/metadata.py", line 542, in distribution
return Distribution.from_name(distribution_name)
  File "/opt/conda/lib/python3.9/importlib/metadata.py", line 196, in from_name
raise PackageNotFoundError(name)
importlib.metadata.PackageNotFoundError: mlflow
```

Fun fact: `importlib.util.find_spec("mlflow") is not None` check in `is_mlflow_available` actually passes for `mlflow-skinny`.
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Fixes #29195


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