return 10 superevents by default for superevents list resource, instead of 3. ...

return 10 superevents by default for superevents list resource, instead of 3.  Matches behavior of events list resource.

gracedb/superevents/api/paginators.py

@@ -63,7 +63,7 @@ class CustomLogTagPagination(pagination.PageNumberPagination):
 
 
 class CustomSupereventPagination(pagination.LimitOffsetPagination):
-    default_limit = 3
+    default_limit = 10
     limit_query_param = 'count'
     offset_query_param = 'start'