No need to cast to list

`sorted` already returns a list

(squash when merging, i'm just on a different computer using web UI so can't do it here)

Author: jeffwidman

kafka/coordinator/assignors/range.py

@@ -46,7 +46,7 @@ def assign(cls, cluster, member_metadata):
             if partitions is None:
                 log.warning('No partition metadata for topic %s', topic)
                 continue
-            partitions = sorted(list(partitions))
+            partitions = sorted(partitions)
             consumers_for_topic.sort()
 
             partitions_per_consumer = len(partitions) // len(consumers_for_topic)