package/python-pytest: remove runtime dependency on python-toml

Since version 7.2 [1], with Python 3.11+ pytest no longer uses tomli to
parse pyproject.toml but instead uses tomllib which is part of Python
itself [2]. Note that toml was replaced with tomli in version 7.0, so
the dependency was anyway incorrect.

Note that tomllib is unconditionally installed as part of Python 3.11,
there is no PYTHON3_LIBTOML option or anything like that that needs to
be selected.

[1] https://docs.pytest.org/en/latest/changelog.html#pytest-7-2-0-2022-10-23
[2] https://github.com/pytest-dev/pytest/pull/9741



Signed-off-by: Arnout Vandecappelle <arnout@mind.be>
Reviewed-by: Ryan Barnett <ryanbarnett3@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>