Restore x-addedInMatrixVersion for room_type

Author: Johennes

data/api/client-server/definitions/room_summary.yaml

@@ -23,6 +23,7 @@ allOf:
         description: The `type` of room (from
           [`m.room.create`](/client-server-api/#mroomcreate)),
           if any.
+        x-addedInMatrixVersion: "1.4"
       allowed_room_ids:
         type: array
         items: