MDEV-30172: Disable galera.galera_parallel_simple

Author: dr-m

mysql-test/suite/galera/disabled.def

@@ -25,3 +25,4 @@ galera_wan : [ERROR] WSREP: /home/buildbot/buildbot/build/gcs/src/gcs_state_msg.
 galera_var_ignore_apply_errors : 28: "Server did not transition to READY state"
 galera_bf_kill_debug : timeout after 900 seconds
 galera_ssl_upgrade : [Warning] Failed to load slave replication state from table mysql.gtid_slave_pos: 130: Incorrect file format 'gtid_slave_pos'
+galera_parallel_simple : timeout related to wsrep_sync_wait