Update tox to 3.24.1

[pyup-bot]

This PR updates tox from 3.24.0 to 3.24.1.

Changelog

3.24.1

--------------------

Bugfixes
^^^^^^^^

- ``get_requires_for_build_sdist`` hook (PEP 517) is assumed to return an empty list if left unimplemented by the backend build system - by :user:`oczkoisse`
`2130 <https://github.com/tox-dev/tox/issues/2130>`_


Documentation
^^^^^^^^^^^^^

- The documentation of ``install_command`` now also mentions that you can provide arbitrary commands - by :user:`jugmac00`
`2081 <https://github.com/tox-dev/tox/issues/2081>`_

Links

• PyPI: https://pypi.org/project/tox
• Changelog: https://pyup.io/changelogs/tox/
• Docs: http://tox.readthedocs.org