Remove redundant initialization

gtk3-theme-prefs.py

@@ -155,9 +155,6 @@ class UndoStack(object):
 
 # FIXME: only save the changed rows, not the whole store
 class UndoableStore(Gtk.ListStore):
-    _stack = UndoStack()
-    _freeze = False
-
     def __init__(self, *args, **kwargs):
         self._stack = UndoStack()
         self._freeze = False