galera.galera_restart_on_unknown_option test regression after MDEV-40023

The test galera.galera_restart_on_unknown_option uses unsupported syntax "try:" in expect file. This has been silently ignored in earlier MariaDB versions, and the test has passed but only after 30 sec sleep.
Since the fix in MDEV-40023, the test started to fail constantly, with error message: "*** ERROR: Unknown command 'try:--galera-unknown-option' in expect file"

galera.galera_restart_on_unknown_option test should be fixed to not use try: option