Second half of little cleanup tweaks suggested by pyflakes.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@3414 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/middleware/cache.py

@@ -1,7 +1,6 @@
 from django.conf import settings
 from django.core.cache import cache
 from django.utils.cache import get_cache_key, learn_cache_key, patch_response_headers
-from django.http import HttpResponseNotModified
 
 class CacheMiddleware(object):
     """