🧲 Use our own require_bitsandbytes

[qgallouedec]

What does this PR do?

To avoid this warning in our tests:

../transformers/src/transformers/testing_utils.py:1163
  /fsx/qgallouedec/transformers/src/transformers/testing_utils.py:1163: PytestUnknownMarkWarning: Unknown pytest.mark.bitsandbytes - is this a typo?  You can register custom marks to avoid this warning - for details, see https://docs.pytest.org/en/stable/how-to/mark.html
    return pytest.mark.bitsandbytes(test_case)

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html

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[HuggingFaceDocBuilderDev]

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[qgallouedec]

Failing test not related (fixed in #2373)