Fix galera_sync_wait_show.test

Since the purpose of event is just to see on second node whether it is
created or not And we are not goint to execute the event also. So instead
of setting GLOBAL event_scheduler=ON and then turning it off,  we can just
disable the warning.

mysql-test/suite/galera/t/galera_sync_wait_show.test

@@ -63,7 +63,9 @@ DROP TABLE t1;
 
 
 --connection node_1
+--disable_warnings
 CREATE EVENT event1 ON SCHEDULE AT '2038-01-01 23:59:59' DO SELECT 1;
+--enable_warnings
 
 --connection node_2
 SHOW CREATE EVENT event1;