py-test-benchmark: updated to 4.0.0

4.0.0 (2022-10-26)
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* Dropped support for legacy Pythons (2.7, 3.6 or older).
* Switched CI to GitHub Actions.
* Removed dependency on the ``py`` library (that was not properly specified as a dependency anyway).
* Fix skipping test in `test_utils.py` if appropriate VCS not available. Also fix typo.
* Added support for pytest 7.2.0 by using ``pytest.hookimpl`` and ``pytest.hookspec`` to configure hooks.
* Now no save is attempted if ``--benchmark-disable`` is used.

(adam)