docs(widgets): drop stale sphinx/html5.py line ref from test comment

The comment in ``_sphinx_native_html`` cited ``writers/html5.py:626-629``
which drifted relative to the installed Sphinx 8.2.3 (actual:
``visit_literal_block`` at 589, ``highlight_block`` call at 603,
``'</div>\n'`` append at 614). Drop the line-number suffix and keep the
class-plus-method anchor -- the latter is a stable API reference that
won't rot. (``_base.py``'s matching reference was updated in the
non-HTML-builder commit.)

Author: tony

tests/docs/test_widgets.py

@@ -287,9 +287,9 @@ def _sphinx_native_html(
     (srcdir / "native.rst").write_text(rst, encoding="utf-8")
     app.build()
     html = (pathlib.Path(app.outdir) / "native.html").read_text(encoding="utf-8")
-    # Match Sphinx's highlight wrapper (writers/html5.py:626-629); the two
-    # trailing ``</div>\n`` (inner Pygments close + outer Sphinx close) anchor
-    # the end of the block.
+    # Match Sphinx's highlight wrapper produced by
+    # ``HTML5Translator.visit_literal_block``; the two trailing ``</div>\n``
+    # (inner Pygments close + outer Sphinx close) anchor the end of the block.
     pattern = re.compile(
         rf'<div class="highlight-{re.escape(language)} notranslate">'
         r".*?</div>\n</div>\n",