chore(deps): update lxml requirement from <5 to <6 (#167)

Updates the requirements on [lxml](https://github.com/lxml/lxml) to
permit the latest version.
<details>
<summary>Changelog</summary>
<p><em>Sourced from <a
href="https://github.com/lxml/lxml/blob/master/CHANGES.txt">lxml's
changelog</a>.</em></p>
<blockquote>
<h1>5.0.0 (2023-12-29)</h1>
<h2>Features added</h2>
<ul>
<li>
<p>Character escaping in <code>C14N2</code> serialisation now uses a
single pass over the text
instead of searching for each unescaped character separately.</p>
</li>
<li>
<p>Early support for Python 3.13a2 was added.</p>
</li>
</ul>
<h2>Bugs fixed</h2>
<ul>
<li>
<p>LP#1976304: The <code>Element.addnext()</code> method previously
inserted the new element
before existing tail text. The tail text of both sibling elements now
stays on
the respective elements.</p>
</li>
<li>
<p>LP#1980767, GH#379: <code>TreeBuilder.close()</code> could fail with
a <code>TypeError</code> after
parsing incorrect input.  Original patch by Enrico Minack.</p>
</li>
<li>
<p><code>Element.itertext(with_tail=False)</code> returned the tail text
of comments and
processing instructions, despite the explicit option.</p>
</li>
<li>
<p>GH#370: A crash with recent libxml2 2.11.x versions was resolved.
Patch by Michael Schlenker.</p>
</li>
<li>
<p>A compile problem with recent libxml2 2.12.x versions was
resolved.</p>
</li>
<li>
<p>The internal exception handling in C callbacks was improved for
Cython 3.0.</p>
</li>
<li>
<p>The exception declarations of <code>xmlInputReadCallback</code>,
<code>xmlInputCloseCallback</code>,
<code>xmlOutputWriteCallback</code> and
<code>xmlOutputCloseCallback</code> in <code>tree.pxd</code> were
corrected to prevent running Python code or calling into the C-API with
a live
exception set.</p>
</li>
<li>
<p>GH#385: The long deprecated <code>unittest.m̀akeSuite()</code>
function is no longer used.
Patch by Miro Hrončok.</p>
</li>
<li>
<p>LP#1522052: A file-system specific test is now optional and should no
longer fail
on systems that don't support it.</p>
</li>
<li>
<p>GH#392: Some tests were adapted for libxml2 2.13.
Patch by Nick Wellnhofer.</p>
</li>
<li>
<p>Contains all fixes from lxml 4.9.4.</p>
</li>
</ul>
<h2>Other changes</h2>
<!-- raw HTML omitted -->
</blockquote>
<p>... (truncated)</p>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/lxml/lxml/commit/73fa11564a8cb814a9da7400449e65790a25105e"><code>73fa115</code></a>
Prepare release of lxml 5.0.0.</li>
<li><a
href="https://github.com/lxml/lxml/commit/625658445f095a76057d9ac5449558b28fa93eb1"><code>6256584</code></a>
Update changelog.</li>
<li><a
href="https://github.com/lxml/lxml/commit/b38cebf2f846e92bd63de4488fd3d1c8b568f397"><code>b38cebf</code></a>
Disable external entity resolution (XXE) by default (<a
href="https://redirect.github.com/lxml/lxml/issues/391">GH-391</a>)</li>
<li><a
href="https://github.com/lxml/lxml/commit/2de6ecf75c0896c83b742dd248494617dd53aa68"><code>2de6ecf</code></a>
tests: Set no_network=False in HTTP tests (<a
href="https://redirect.github.com/lxml/lxml/issues/392">GH-392</a>)</li>
<li><a
href="https://github.com/lxml/lxml/commit/5024820445f50ba576605b26f23c1a9ffe179e4a"><code>5024820</code></a>
Minor code cleanup.</li>
<li><a
href="https://github.com/lxml/lxml/commit/9f58aa763e57cc5f2facbf482f447c318f676774"><code>9f58aa7</code></a>
Do not let &quot;Element.itertext()&quot;&quot; return tail text of PIs
and comments if the ...</li>
<li><a
href="https://github.com/lxml/lxml/commit/badcb49c2f6d5d80e157ff6754b9756937631e9e"><code>badcb49</code></a>
Update changelog.</li>
<li><a
href="https://github.com/lxml/lxml/commit/e82b1f583fb04b79a6616934af3a2c4a7f9504c5"><code>e82b1f5</code></a>
CI: Build the coverage job with STATIC_DEPS=true to make it independent
of th...</li>
<li><a
href="https://github.com/lxml/lxml/commit/8324137aa8b014c168cf2a20b617599fc614fac5"><code>8324137</code></a>
Fix test in Py2.7.</li>
<li><a
href="https://github.com/lxml/lxml/commit/ac828388ab5308b39f59bd836201b66d158001ac"><code>ac82838</code></a>
Fix the work around for a test failure in Python 3.11.</li>
<li>Additional commits viewable in <a
href="https://github.com/lxml/lxml/compare/lxml-0.5.1...lxml-5.0.0">compare
view</a></li>
</ul>
</details>
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requirements.txt

@@ -1,5 +1,5 @@
 ansible-core>=2.15,<2.15.5
 graphviz>=0.18,<1
 colour<1
-lxml<5
+lxml<6
 svg.path<7