We have no html5lib packaged yet.

--- sphinxcontrib_htmlhelp-2.1.0/tests/test_htmlhelp.py.orig
+++ sphinxcontrib_htmlhelp-2.1.0/tests/test_htmlhelp.py
@@ -7,7 +7,6 @@
 from typing import TYPE_CHECKING
 
 import pytest
-from html5lib import HTMLParser
 from sphinx.config import Config
 
 from sphinxcontrib.htmlhelp import chm_htmlescape, default_htmlhelp_basename
@@ -73,52 +72,6 @@
     assert m is None, 'Hex escaping exists in .hhk file: ' + str(m.group(0))
 
 
-@pytest.mark.sphinx('htmlhelp', testroot='hhc')
-def test_htmlhelp_hhc(app: Sphinx) -> None:
-    app.build()
-
-    def assert_sitemap(node: Element, name: str, filename: str) -> None:
-        assert node.tag == 'object'
-        assert len(node) == 2
-        assert node[0].tag == 'param'
-        assert node[0].attrib == {'name': 'Name',  'value': name}
-        assert node[1].tag == 'param'
-        assert node[1].attrib == {'name': 'Local', 'value': filename}
-
-    # .hhc file
-    hhc = (app.outdir / 'pythondoc.hhc').read_text(encoding='utf-8')
-    tree = HTMLParser(namespaceHTMLElements=False).parse(hhc)
-    items = tree.find('.//body/ul')
-    assert len(items) == 4
-
-    # index
-    assert items[0].tag == 'li'
-    assert len(items[0]) == 1
-    assert_sitemap(items[0][0], "Sphinx's documentation", 'index.html')
-
-    # py-modindex
-    assert items[1].tag == 'li'
-    assert len(items[1]) == 1
-    assert_sitemap(items[1][0], 'Python Module Index', 'py-modindex.html')
-
-    # toctree
-    assert items[2].tag == 'li'
-    assert len(items[2]) == 2
-    assert_sitemap(items[2][0], 'foo', 'foo.html')
-
-    assert items[2][1].tag == 'ul'
-    assert len(items[2][1]) == 1
-    assert items[2][1][0].tag == 'li'
-    assert_sitemap(items[2][1][0][0], 'bar', 'bar.html')
-
-    assert items[3].tag == 'li'
-    assert len(items[3]) == 1
-    assert_sitemap(items[3][0], 'baz', 'baz.html')
-
-    # single quotes should be escaped as decimal (')
-    assert "Sphinx's documentation" in hhc
-
-
 def test_chm_htmlescape() -> None:
     assert chm_htmlescape('Hello world') == 'Hello world'
     assert chm_htmlescape('Unicode 文字') == 'Unicode 文字'
--- sphinxcontrib_htmlhelp-2.1.0/pyproject.toml.orig
+++ sphinxcontrib_htmlhelp-2.1.0/pyproject.toml
@@ -45,7 +45,6 @@
 [project.optional-dependencies]
 test = [
     "pytest",
-    "html5lib",
 ]
 lint = [
     "ruff==0.5.5",