Small metadata naming fix

common/lib/xmodule/xmodule/templates/combinedopenended/default.yaml

 ---
 metadata:
     display_name: Open Ended Response
-    attempts: 1
+    max_attempts: 1
     max_score: 1
     is_graded: False
     version: 1

common/lib/xmodule/xmodule/templates/peer_grading/default.yaml

@@ -5,6 +5,7 @@ metadata:
     use_for_single_location: False
     link_to_location: None
     is_graded: False
+    max_grade: 1
 data: |
   <peergrading>
   </peergrading>