Build(deps-dev): Update tox requirement from >=4.56.2 to >=4.56.4 (#354)

Updates the requirements on [tox](https://github.com/tox-dev/tox) to
permit the latest version.
<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>v4.56.4</h2>
<!-- raw HTML omitted -->
<h2>What's Changed</h2>
<ul>
<li>🐛 fix(discovery): find debug interpreters like python3.13-dbg by <a
href="https://github.com/gaborbernat"><code>@​gaborbernat</code></a> in
<a
href="https://redirect.github.com/tox-dev/tox/pull/3978">tox-dev/tox#3978</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/tox-dev/tox/compare/4.56.3...4.56.4">https://github.com/tox-dev/tox/compare/4.56.3...4.56.4</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>
<h1>Bug fixes - 4.56.4</h1>
<ul>
<li>Discover debug (<code>Py_DEBUG</code>) interpreters set as
<code>base_python</code>, such as Debian's <code>python3.13-dbg</code> -
the spec was
misread as a machine named <code>dbg</code> and no interpreter matched.
Requires <code>python-discovery&gt;=1.4.4</code> - by
:user:<code>gaborbernat</code>. (:issue:<code>3977</code>)</li>
</ul>
<hr />
<p>v4.56.3 (2026-07-08)</p>
<hr />
<h1>Bug fixes - 4.56.3</h1>
<ul>
<li>Stop double-closing the child pty file descriptor when running under
a tty, which could race a parallel run that had
reused the freed descriptor number and cause intermittent <code>Bad file
descriptor</code>/<code>Input/output error</code> failures - by
:user:<code>apoorvdarshan</code>. (:issue:<code>3975</code>)</li>
</ul>
<hr />
<p>v4.56.2 (2026-07-07)</p>
<hr />
<h1>Bug fixes - 4.56.2</h1>
<ul>
<li>
<p>Fix a batch of latent defects found in a codebase audit:</p>
<ul>
<li>stop duplicating <code>--extra-index-url</code> when a merged
requirements line repeats an already-seen index;</li>
<li>render <code>--no-binary</code>/<code>--only-binary</code> as
comma-joined strings instead of leaking the internal <code>set</code>
into the
pip command line;</li>
<li>report a clear error instead of <code>IndexError</code> for a bare
one-argument flag (<code>-c</code>, <code>-r</code>, <code>-f</code>,
<code>-e</code>) in
<code>deps</code> or constraints;</li>
<li>canonicalize <code>optional-dependencies</code> keys and
self-referential (recursive) extra names so non-canonical spellings
no longer silently drop dependencies;</li>
<li>raise a clear error instead of <code>KeyError</code> when
<code>dependency_groups</code> is requested without a
<code>[dependency-groups]</code> table;</li>
<li>stop a native TOML <code>{ replace = &quot;env&quot; }</code>
reference from leaking its resolution chain into sibling list entries
and
tripping a spurious <code>circular chain</code> error;</li>
<li>expand the range that actually matched in a factor expression rather
than the first identical digit-range substring;</li>
<li>strip the backslash from an escaped <code>\;</code> in
<code>set_env</code> values;</li>
<li>skip option values during command auto-detection so an environment
named like a subcommand (e.g. <code>tox -e list</code>) is
no longer misread;</li>
<li>treat an empty list-typed environment variable (e.g.
<code>TOX_DISCOVER=</code>) as an empty list rather than
<code>[&quot;&quot;]</code>;</li>
<li>report an environment whose name is an empty string as present in
<code>Config</code> membership tests;</li>
<li>fail evaluation gracefully instead of crashing the driver thread
when <code>tox p -p all</code> is run with an empty
selection;</li>
<li>avoid rebuilding a throwaway PEP 517 frontend against the previous
root when a package environment's <code>root</code> is
reassigned before a frontend exists;</li>
<li>avoid crashing <code>create_session_view</code> when the package and
its session copy share no common path (e.g. different
Windows drives);</li>
</ul>
</li>
</ul>
<!-- raw HTML omitted -->
</blockquote>
<p>... (truncated)</p>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/tox-dev/tox/commit/a44a942760af018c40af3c2825e214b0c7c776c0"><code>a44a942</code></a>
release 4.56.4</li>
<li><a
href="https://github.com/tox-dev/tox/commit/779050178871507412c0efff947f9e154355ea01"><code>7790501</code></a>
🐛 fix(discovery): find debug interpreters like python3.13-dbg (<a
href="https://redirect.github.com/tox-dev/tox/issues/3978">#3978</a>)</li>
<li><a
href="https://github.com/tox-dev/tox/commit/4dac7feadada17511380f9a0af2a1d250d12091b"><code>4dac7fe</code></a>
release 4.56.3</li>
<li><a
href="https://github.com/tox-dev/tox/commit/6f8dabccf8773938368aabcbe44362afcc7928c7"><code>6f8dabc</code></a>
Don't double-close the child pty fd (fixes parallel Bad file descriptor)
(<a
href="https://redirect.github.com/tox-dev/tox/issues/39">#39</a>...</li>
<li>See full diff in <a
href="https://github.com/tox-dev/tox/compare/4.56.2...4.56.4">compare
view</a></li>
</ul>
</details>
<br />


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</details>

Author: Diapolo10

pyproject.toml

@@ -50,7 +50,7 @@ dev = [
     "pytest-xdist[psutil]>=3.8.0",
     "ruff>=0.15.20",
     "sphinx>=9.0.4",
-    "tox>=4.56.2",
+    "tox>=4.56.4",
     "tox-gh-actions>=3.5.0",
 ]