Bump tox from 4.28.3 to 4.28.4 (#540)

Bumps [tox](https://github.com/tox-dev/tox) from 4.28.3 to 4.28.4.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/tox-dev/tox/releases">tox's
releases</a>.</em></p>
<blockquote>
<h2>4.28.4</h2>
<!-- raw HTML omitted -->
<h2>What's Changed</h2>
<ul>
<li>[pre-commit.ci] pre-commit autoupdate by <a
href="https://github.com/pre-commit-ci"><code>@​pre-commit-ci</code></a>[bot]
in <a
href="https://redirect.github.com/tox-dev/tox/pull/3570">tox-dev/tox#3570</a></li>
<li>Pass ssh-agent variables by default by <a
href="https://github.com/daniilgankov"><code>@​daniilgankov</code></a>
in <a
href="https://redirect.github.com/tox-dev/tox/pull/3572">tox-dev/tox#3572</a></li>
</ul>
<h2>New Contributors</h2>
<ul>
<li><a
href="https://github.com/daniilgankov"><code>@​daniilgankov</code></a>
made their first contribution in <a
href="https://redirect.github.com/tox-dev/tox/pull/3572">tox-dev/tox#3572</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/tox-dev/tox/compare/4.28.3...4.28.4">https://github.com/tox-dev/tox/compare/4.28.3...4.28.4</a></p>
</blockquote>
</details>
<details>
<summary>Changelog</summary>
<p><em>Sourced from <a
href="https://github.com/tox-dev/tox/blob/main/docs/changelog.rst">tox's
changelog</a>.</em></p>
<blockquote>
<h2>v4.28.4 (2025-07-31)</h2>
<p>Features - 4.28.4</p>
<pre><code>- Pass ssh-agent variables ``SSH_AGENT_PID`` and
``SSH_AUTH_SOCK`` in ``pass_env`` by default.
  - by :user:`daniilgankov` (:issue:`3572`)
</code></pre>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/tox-dev/tox/commit/611b7516d639638cecb1e2117adeeb6567120438"><code>611b751</code></a>
release 4.28.4</li>
<li><a
href="https://github.com/tox-dev/tox/commit/9f2db71b64bdfc90ce40b33b38df82ac4d1a2abc"><code>9f2db71</code></a>
Pass ssh-agent variables by default (<a
href="https://redirect.github.com/tox-dev/tox/issues/3572">#3572</a>)</li>
<li><a
href="https://github.com/tox-dev/tox/commit/c28c4b1c37b6cb24c66be2667223961cf14feaae"><code>c28c4b1</code></a>
[pre-commit.ci] pre-commit autoupdate (<a
href="https://redirect.github.com/tox-dev/tox/issues/3570">#3570</a>)</li>
<li>See full diff in <a
href="https://github.com/tox-dev/tox/compare/4.28.3...4.28.4">compare
view</a></li>
</ul>
</details>
<br />


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Author: dependabot[bot]

requirements-dev.txt

@@ -5,5 +5,5 @@ pytest==8.4.1
 pytest-aiohttp==0.3.0
 pytest-cov==6.2.1
 selenium==4.34.0
-tox==4.28.3
+tox==4.28.4
 urllib3==2.4.0  # for selenium