Fix missing migration from _description to __doc__

trytond/model/modelsql.py

@@ -1047,7 +1047,8 @@ class ModelSQL(ModelStorage):
                 if rowcount == -1 or rowcount is None:
                     rowcount = len(cursor.fetchall())
                 if not rowcount == len({}.fromkeys(sub_ids)):
-                    cls.raise_user_error('access_error', cls._description)
+                    cls.raise_user_error('access_error',
+                        cls.__doc__.splitlines()[0])
 
         cls.trigger_delete(records)