build(deps-dev): update tox requirement from ~=4.20.0 to ~=4.21.1 in the python-packages group across 1 directory

[dependabot]

Updates the requirements on tox to permit the latest version.
Updates tox to 4.21.1

Release notes

Sourced from tox's releases.

4.21.1

What's Changed

• Fix TOML configuration errors by @​gaborbernat in tox-dev/tox#3388

Full Changelog: tox-dev/tox@4.21.0...4.21.1

Changelog

Sourced from tox's changelog.

v4.21.1 (2024-10-02)

Bugfixes - 4.21.1

- Fix error when using ``requires`` within a TOML configuration file - by :user:`gaborbernat`. (:issue:`3386`)
- Fix error when using ``deps`` within a TOML configuration file - by :user:`gaborbernat`. (:issue:`3387`)
- Multiple fixes for the TOML configuration by :user:`gaborbernat`.:

Do not fail when there is an empty command within commands.
Allow references for set_env by accepting list of dictionaries for it.
Do not try to be smart about reference unrolling, instead allow the user to control it via the extend flag,
available both for posargs and ref replacements.
The ref replacements raw key has been renamed to of. (:issue:3388)

v4.21.0 (2024-09-30)
Features - 4.21.0

• Native TOML configuration support - by :user:gaborbernat. (:issue:999)

Improved Documentation - 4.21.0

- Update Loader docs - by :user:ziima (:issue:`3352`)
v4.20.0 (2024-09-18)
Features - 4.20.0
- Separate the list dependencies functionality to a separate abstract class allowing code reuse in plugins (such as
  ``tox-uv``) - by :gaborbernat`. (:issue:`3347`)
v4.19.0 (2024-09-17)
Features - 4.19.0



Support pypy-<major>.<minor> environment names for PyPy environments - by :user:gaborbernat. (:issue:3346)

v4.18.1 (2024-09-07)
Bugfixes - 4.18.1
- Fix and test the string spec for the ``sys.executable`` interpreter (introduced in :pull:`3325`)
  - by :user:`hroncok` (:issue:`3327`)
Improved Documentation - 4.18.1

</tr></table>

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</details>

<details>

<summary>Commits</summary>
<ul>

<li><a href="https://github.com/tox-dev/tox/commit/434ac18d89a843b961c8544bf74e796191c940f0&quot;&gt;&lt;code&gt;434ac18&lt;/code&gt;&lt;/a> release 4.21.1</li>

<li><a href="https://github.com/tox-dev/tox/commit/34d3adc0ed537de5d4803b4e244e43eed513c839&quot;&gt;&lt;code&gt;34d3adc&lt;/code&gt;&lt;/a> Fix TOML configuration errors (<a href="https://redirect.github.com/tox-dev/tox/issues/3388&quot;&gt;#3388&lt;/a&gt;)&lt;/li>

<li><a href="https://github.com/tox-dev/tox/commit/719b3462b58bd5c4fc12d93cb978f824bc7a610b&quot;&gt;&lt;code&gt;719b346&lt;/code&gt;&lt;/a> Update installation.rst</li>

<li><a href="https://github.com/tox-dev/tox/commit/46bef9eff54c53eeced031436d2d1a068b4bfb16&quot;&gt;&lt;code&gt;46bef9e&lt;/code&gt;&lt;/a> release 4.21.0</li>

<li><a href="https://github.com/tox-dev/tox/commit/cea105b7007039c830c92ae92aa5792e819ee487&quot;&gt;&lt;code&gt;cea105b&lt;/code&gt;&lt;/a> True TOML config support (<a href="https://redirect.github.com/tox-dev/tox/issues/3353&quot;&gt;#3353&lt;/a&gt;)&lt;/li>

<li><a href="https://github.com/tox-dev/tox/commit/a04b039fe0486752ec79733b993d73ecdf282795&quot;&gt;&lt;code&gt;a04b039&lt;/code&gt;&lt;/a> [pre-commit.ci] pre-commit autoupdate (<a href="https://redirect.github.com/tox-dev/tox/issues/3385&quot;&gt;#3385&lt;/a&gt;)&lt;/li>

<li><a href="https://github.com/tox-dev/tox/commit/f5eba31ed3aeedcb41db64fca5b624a75abff32d&quot;&gt;&lt;code&gt;f5eba31&lt;/code&gt;&lt;/a> Update Loader docs (<a href="https://redirect.github.com/tox-dev/tox/issues/3352&quot;&gt;#3352&lt;/a&gt;)&lt;/li>

<li><a href="https://github.com/tox-dev/tox/commit/329db639b5573cf9b5990fe990a3e48789d1fc9a&quot;&gt;&lt;code&gt;329db63&lt;/code&gt;&lt;/a> [pre-commit.ci] pre-commit autoupdate (<a href="https://redirect.github.com/tox-dev/tox/issues/3350&quot;&gt;#3350&lt;/a&gt;)&lt;/li>

<li><a href="https://github.com/tox-dev/tox/commit/f4b3bd20f268e6da78c2a89b531f364cec35b90b&quot;&gt;&lt;code&gt;f4b3bd2&lt;/code&gt;&lt;/a> Bump pypa/gh-action-pypi-publish from 1.10.1 to 1.10.2 (<a href="https://redirect.github.com/tox-dev/tox/issues/3349&quot;&gt;#3349&lt;/a&gt;)&lt;/li>

<li>See full diff in <a href="https://github.com/tox-dev/tox/compare/4.20.0...4.21.1&quot;&gt;compare view</a></li>

</ul>

</details>
<br />


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