don't return, update docstring

Author: trel

irods/manager/zone_manager.py

@@ -60,12 +60,7 @@ def zone_report(self):
         return response.get_json_encoded_struct()
 
     def modify(self, zone_name, attribute, value):
-        """
-        Modify a zone attribute.
-
-        Returns:
-            The modified zone.
-        """
+        """Modify a zone attribute."""
         if attribute == "connection":
             attribute = "conn"  # server expects this string
         message_body = GeneralAdminRequest("modify", "zone", zone_name, attribute, value)