Get rid of supportsTransactionalUndo check. It's not needed any more.

src/ZEO/tests/Cache.py

@@ -34,11 +34,6 @@ class TransUndoStorageWithCache:
             info = self._storage.undoInfo(0, 20)
         tid = info[0]['id']
 
-        # We may need to bail at this point if the storage doesn't
-        # support transactional undo
-        if not self._storage.supportsTransactionalUndo():
-            return
-
         # Now start an undo transaction
         t = Transaction()
         t.note('undo1')