Fix an HTML-parser test that's failed in Python 2.6.8 since 5c79dd58.

The problem description in #18239 asserted that
http://bugs.python.org/issue670664 was fixed in Python 2.6.8, but based on
http://bugs.python.org/issue670664#msg146770 it appears that's not correct; the
fix was only applied in 2.7, 3.2, and Python trunk. Therefore we must use our
patched HTMLParser subclass in all Python 2.6 versions.

django/utils/html_parser.py

@@ -5,8 +5,7 @@ import sys
 current_version = sys.version_info
 
 use_workaround = (
-    (current_version < (2, 6, 8)) or
-    (current_version >= (2, 7) and current_version < (2, 7, 3)) or
+    (current_version < (2, 7, 3)) or
     (current_version >= (3, 0) and current_version < (3, 2, 3))
 )