fixed import of MIN_HANCHANS_FOR_LADDER that moved to settings

src/mahjong_ranking/middleware.py

@@ -1,8 +1,7 @@
 """Middleware to defer slow denormalization  at the end of a request."""
 from django.core.cache import cache
-
 from mahjong_ranking import models
-from . import LOGGER, MIN_HANCHANS_FOR_LADDER
+from . import LOGGER
 
 
 class DenormalizationUpdateMiddleware(object):  # Ignore PyLintBear (R0903)