chore: Add another scenario to illegal_entities test

Co-authored-by: Adrián Chaves <[email protected]>

Author: Laerte

tests/test_html.py

@@ -66,6 +66,7 @@ def test_illegal_entities(self):
         self.assertEqual(replace_entities("xy"), "xy")
         self.assertEqual(replace_entities("xy", remove_illegal=False), "xy")
         self.assertEqual(replace_entities("�"), "")
+        self.assertEqual(replace_entities("�", remove_illegal=False), "�")
 
     def test_browser_hack(self):
         # check browser hack for numeric character references in the 80-9F range