Fix typing annotation in hf_argparser

[xu-song]

What does this PR do?

Fix typing annotation in hf_argparser.

The following code raise warning in IDE: Expected type 'str', got 'Path' instead

transformers/tests/utils/test_hf_argparser.py

Line 382 in 6cdbd73

parsed_args = parser.parse_yaml_file(Path(temp_local_path + ".json"))[0]

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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• Did you make sure to update the documentation with your changes? Here are the
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  here are tips on formatting docstrings.
• Did you write any new necessary tests?

Who can review?

Library:

• pipelines: @Narsil
• trainer: @muellerzr and @pacman100

Documentation: @stevhliu and @MKhalusova

[amyeroberts]

Thanks!