Fixed typo in BaseCache.delete_many() docstring.

django/core/cache/backends/base.py

@@ -216,7 +216,7 @@ class BaseCache(object):
 
     def delete_many(self, keys, version=None):
         """
-        Set a bunch of values in the cache at once.  For certain backends
+        Delete a bunch of values in the cache at once. For certain backends
         (memcached), this is much more efficient than calling delete() multiple
         times.
         """