Drop pytest-flake8 from test requirements to fix CI on pytest 9 - #137

The CI testing workflow currently fails on every OS before a single test is collected:

pluggy._manager.PluginValidationError: Plugin 'flake8' for hook 'pytest_collect_file'
hookimpl definition: pytest_collect_file(file_path, path, parent)
Argument(s) {'path'} are declared in the hookimpl but can not be found in the hookspec

pytest 9 removed the legacy py.path path hook argument, and the latest pytest-flake8 (1.3.0) still declares it, so pytest refuses to load the plugin. Nothing in the repo actually uses it (--flake8 isn't in addopts, and linting runs through ruff in pre-commit), so this just removes it from tests/requirements.txt. The standalone flake8 entry is left as is.

Tested locally on Python 3.11 with the same versions as the failing run (pytest 9.1.1, torch 2.14.1, transformers 5.18.0, datasets 5.1.0):

• before: pytest src tests fails with the error above
• after: 15 passed

Summary by CodeRabbit

• Chores
  • Removed a linting tool from the test environment requirements. The remaining listed requirements are unchanged, and this update does not change end-user functionality.