Update sphinx-rtd-theme requirement from <3,>=1 to >=1,<4 in /requirements (#53)

Updates the requirements on
[sphinx-rtd-theme](https://github.com/readthedocs/sphinx_rtd_theme) to
permit the latest version.
<details>
<summary>Changelog</summary>
<p><em>Sourced from <a
href="https://github.com/readthedocs/sphinx_rtd_theme/blob/master/docs/changelog.rst">sphinx-rtd-theme's
changelog</a>.</em></p>
<blockquote>
<h1>3.0.1</h1>
<ul>
<li>Use black color for text in selectors.</li>
</ul>
<p>.. _release-3.0.0:</p>
<h1>3.0.0</h1>
<p>Final version.</p>
<p>.. _release-3.0.0rc4:</p>
<h1>3.0.0rc4</h1>
<h2>Fixes</h2>
<ul>
<li>Trigger &quot;Read the Docs Search addon&quot; when focusing the
&quot;Search docs&quot; input in the navbar.</li>
</ul>
<p>.. _release-3.0.0rc3:</p>
<h1>3.0.0rc3</h1>
<h2>Fixes</h2>
<ul>
<li>Show hidden version in selector if it's the current active
version</li>
</ul>
<p>.. _release-3.0.0rc2:</p>
<h1>3.0.0rc2</h1>
<h2>Added</h2>
<ul>
<li>Render version and language selectors below the documentation's
title (top left).
This can be controlled via the new theme options
<code>version_selector</code> and <code>language_selector</code>.</li>
</ul>
<p>.. _release-3.0.0rc1:</p>
<h1>3.0.0rc1</h1>
<h2>Added</h2>
<!-- raw HTML omitted -->
</blockquote>
<p>... (truncated)</p>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/readthedocs/sphinx_rtd_theme/commit/7b894f5e7a5053dd35de406bc779020c229f20a9"><code>7b894f5</code></a>
Release 3.0.1</li>
<li><a
href="https://github.com/readthedocs/sphinx_rtd_theme/commit/1f2439c7bf799275d46be82ac004725aff80afbf"><code>1f2439c</code></a>
Use <code>black</code> color for switcher options (<a
href="https://redirect.github.com/readthedocs/sphinx_rtd_theme/issues/1615">#1615</a>)</li>
<li><a
href="https://github.com/readthedocs/sphinx_rtd_theme/commit/a1c2147b17cbf0e57b7d7a6450ad4d9a5ff362cf"><code>a1c2147</code></a>
Release 3.0.0</li>
<li><a
href="https://github.com/readthedocs/sphinx_rtd_theme/commit/814686ee1fa8683fad58d97e56ed71321462d80f"><code>814686e</code></a>
Release 3.0.0rc4</li>
<li><a
href="https://github.com/readthedocs/sphinx_rtd_theme/commit/5b181b89fbe8cf01d12fcb55ec50d81560975eac"><code>5b181b8</code></a>
Trigger search modal on &quot;Search docs&quot; input focus (<a
href="https://redirect.github.com/readthedocs/sphinx_rtd_theme/issues/1610">#1610</a>)</li>
<li><a
href="https://github.com/readthedocs/sphinx_rtd_theme/commit/7deb68fe1631b6bbd015dfbfe2b0b27f9be0fef7"><code>7deb68f</code></a>
Release 3.0.0rc3</li>
<li><a
href="https://github.com/readthedocs/sphinx_rtd_theme/commit/036a3b223170465586e5269bbbc4a834f6ee5a99"><code>036a3b2</code></a>
Show hidden version in selector if it's the current active version (<a
href="https://redirect.github.com/readthedocs/sphinx_rtd_theme/issues/1609">#1609</a>)</li>
<li><a
href="https://github.com/readthedocs/sphinx_rtd_theme/commit/ccf31144c997954aaa9b50839d670b0d282ae824"><code>ccf3114</code></a>
Release 3.0.0rc2 (<a
href="https://redirect.github.com/readthedocs/sphinx_rtd_theme/issues/1607">#1607</a>)</li>
<li><a
href="https://github.com/readthedocs/sphinx_rtd_theme/commit/4cab02fff8850ffbcf4e1c34d9946ac617332ef4"><code>4cab02f</code></a>
Show version/language selectors below the title (<a
href="https://redirect.github.com/readthedocs/sphinx_rtd_theme/issues/1601">#1601</a>)</li>
<li><a
href="https://github.com/readthedocs/sphinx_rtd_theme/commit/9c75444a7399bafc32a6edc1c3524505791e8f39"><code>9c75444</code></a>
Docs: do not sign Git tag (<a
href="https://redirect.github.com/readthedocs/sphinx_rtd_theme/issues/1596">#1596</a>)</li>
<li>Additional commits viewable in <a
href="https://github.com/readthedocs/sphinx_rtd_theme/compare/1.0.0...3.0.1">compare
view</a></li>
</ul>
</details>
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</details>

Author: Guts

requirements/documentation.txt

@@ -4,4 +4,4 @@
 myst-parser[linkify]>=1,<4.1
 sphinx-autobuild==2024.*
 sphinx-copybutton>=0.2,<1
-sphinx-rtd-theme>=1,<3
+sphinx-rtd-theme>=1,<4