fix: avoid newer EnumType for python <= 3.10

per https://docs.python.org/3/library/enum.html#enum.EnumType

src/wuttaweb/grids/filters.py

@@ -27,7 +27,11 @@ Grid Filters
 import datetime
 import logging
 from collections import OrderedDict
-from enum import EnumType
+try:
+    from enum import EnumType
+except ImportError: # pragma: no cover
+    # nb. python <= 3.10
+    from enum import EnumMeta as EnumType
 
 import sqlalchemy as sa