Build(deps-dev): Update tox requirement from >=4.56.0 to >=4.56.1 (#345)

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>v4.56.1</h2>
<!-- raw HTML omitted -->
<h2>What's Changed</h2>
<ul>
<li>treat scalar string then/else as a single item in if-replace extend
by <a href="https://github.com/HrachShah"><code>@​HrachShah</code></a>
in <a
href="https://redirect.github.com/tox-dev/tox/pull/3969">tox-dev/tox#3969</a></li>
</ul>
<h2>New Contributors</h2>
<ul>
<li><a href="https://github.com/HrachShah"><code>@​HrachShah</code></a>
made their first contribution in <a
href="https://redirect.github.com/tox-dev/tox/pull/3969">tox-dev/tox#3969</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/tox-dev/tox/compare/4.56.0...4.56.1">https://github.com/tox-dev/tox/compare/4.56.0...4.56.1</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 - 4.56.1</h1>
<ul>
<li>Fix <code>{ replace = &quot;if&quot; ... extend = true }</code>
corrupting the resulting list when <code>then</code> or
<code>else</code> is a scalar
string (e.g. <code>then = &quot;-v&quot;</code>): a non-empty scalar
string is now appended as a single element instead of being iterated
character-by-character, while a false <code>if</code> with no
<code>else</code> (yielding <code>&quot;&quot;</code>) contributes
nothing rather than an
empty element, and list/set results are still spread into the parent.
(:issue:<code>3969</code>)</li>
</ul>
<hr />
<p>v4.56.0 (2026-06-23)</p>
<hr />
<h1>Features - 4.56.0</h1>
<ul>
<li>Derive :ref:<code>virtualenv_spec</code> automatically: when an
environment targets a Python version the installed
:pypi:<code>virtualenv</code> can no longer create (e.g.
<code>py38</code> with virtualenv <code>21.5+</code>), tox now pins the
newest virtualenv
that still supports it and bootstraps it for that environment only. The
downgrade happens only when every
<code>base_python</code> candidate is unsupported, so environments
targeting current interpreters are unaffected. This fixes
<code>py38</code> (and other end-of-life interpreters) being silently
skipped after a virtualenv upgrade - by
:user:<code>gaborbernat</code>. (:issue:<code>3965</code>)
(:issue:<code>3965</code>)</li>
</ul>
<h1>Bug fixes - 4.56.0</h1>
<ul>
<li>The default value of <code>skip_missing_interpreters</code> changed
from <code>True</code> to <code>False</code> — missing interpreters now
fail
the run by default, matching tox 3 behavior. The tox 4 rewrite
unintentionally changed this default. To restore the
previous (incorrect) behavior, set <code>skip_missing_interpreters =
true</code> in your tox configuration or pass
<code>--skip-missing-interpreters</code> on the command line.
(:issue:<code>3965</code>)</li>
</ul>
<h1>Improved documentation - 4.56.0</h1>
<ul>
<li>Fix nested list items being rendered with continued numbering
instead of as sub-items in <code>development.rst</code>,
<code>onboarding.rst</code> and <code>explanation.rst</code>.
(:issue:<code>3960</code>)</li>
<li>Replace stale <code>http://tox.readthedocs.org</code> URL with
<code>https://tox.wiki</code> in <code>pyproject.toml</code>
(<code>Homepage</code>),
<code>.github/CONTRIBUTING.md</code>, and
<code>.github/PULL_REQUEST_TEMPLATE.md</code>.
(:issue:<code>3963</code>)</li>
</ul>
<hr />
<p>v4.55.1 (2026-06-03)</p>
<hr />
<h1>Bug fixes - 4.55.1</h1>
<ul>
<li><code>TOX_OVERRIDE</code> (and
<code>-x</code>/<code>--override</code>) now propagates through
configuration references. Previously, overriding a
base value that was later referenced via <code>{[section]key}</code>
(ini) or <code>{replace = &quot;ref&quot;, of = [...]}</code> (toml) was
ignored because reference resolution read the raw file value, bypassing
the override system - by
:user:<code>tales-aparecida</code>. (:issue:<code>3950</code>)
(:issue:<code>3950</code>)</li>
</ul>
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</blockquote>
<p>... (truncated)</p>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/tox-dev/tox/commit/4bb64210e056ea35fb123faae08cb23cc08234cb"><code>4bb6421</code></a>
release 4.56.1</li>
<li><a
href="https://github.com/tox-dev/tox/commit/ca2f561b60f30c03c8c0d5386c85f509d45a155b"><code>ca2f561</code></a>
treat scalar string then/else as a single item in if-replace extend (<a
href="https://redirect.github.com/tox-dev/tox/issues/3969">#3969</a>)</li>
<li><a
href="https://github.com/tox-dev/tox/commit/f933bd2ad3028148a9158b74b63920585bf46e36"><code>f933bd2</code></a>
build(deps): bump actions/checkout from 6.0.3 to 7.0.0 (<a
href="https://redirect.github.com/tox-dev/tox/issues/3968">#3968</a>)</li>
<li>See full diff in <a
href="https://github.com/tox-dev/tox/compare/4.56.0...4.56.1">compare
view</a></li>
</ul>
</details>
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Author: Diapolo10