Fix can_map_over for mapping over paired inputs

We'd only try mapping over the first collection type description
otherwise. I suppose we didn't notice because the first type is `list`
and therefore much more common. Noticed this while working on #5640.

lib/galaxy/tools/parameters/history_query.py

@@ -53,4 +53,4 @@ def can_map_over(self, hdca):
             # See note about the way this is sorted above.
             if collection_type_description.is_subcollection_of_type(hdca_collection_type):
                 return collection_type_description
-            return False
+        return False