Modify the table t_ds_worker_group to add a description field in the postgresql upgrade script (#12883)

dolphinscheduler-dao/src/main/resources/sql/upgrade/3.1.1_schema/postgresql/dolphinscheduler_ddl.sql

@@ -30,5 +30,4 @@ END IF;
 END $$;
 
 --- add column
-ALTER TABLE t_ds_task_group alter COLUMN description type varchar(255);
-
+ALTER TABLE t_ds_worker_group ADD COLUMN IF NOT EXISTS description varchar(255) DEFAULT NULL;