Update tox to 3.26.0

[pyup-bot]

This PR updates tox from 3.25.1 to 3.26.0.

Changelog

3.26.0

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

Bugfixes
^^^^^^^^

- Fix fallback to ``python`` environment when ``isolated_build = true`` is set -- by :user:`Unrud`
`2474 <https://github.com/tox-dev/tox/issues/2474>`_
- Fixed ``SetuptoolsDeprecationWarning`` about using ``--global-option`` -- by :user:`adamchainz`
`2478 <https://github.com/tox-dev/tox/issues/2478>`_


Features
^^^^^^^^

- Use ``tomllib`` on Python 3.11 or later and ``tomli`` instead of ``toml`` library on lower versions - by :user:`hroncok`.
`2463 <https://github.com/tox-dev/tox/issues/2463>`_

Links

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