usermanagement: fixed rights to view parent groups of public group

vispa/controller/usermanagement.py

@@ -354,7 +354,7 @@ class UMAjaxController(AbstractController):
         }, assocs=[
             AssociationController(table=User, assoc="manager", rights=rights_manager),
             AssociationToGroupController(table=Group, assoc="parent_group", rights={
-                "list": (Rights.member,),
+                "list": (Rights.public,),
                 "__default__": (Rights.forbidden,),
             }),
         ] + [