Added missing comma in LocMemCache example.

docs/topics/cache.txt

@@ -301,7 +301,7 @@ example::
     CACHES = {
         'default': {
             'BACKEND': 'django.core.cache.backends.locmem.LocMemCache',
-            'LOCATION': 'unique-snowflake'
+            'LOCATION': 'unique-snowflake',
         }
     }