Fixing test case that is sporadically failing.

mysql-test/suite/rpl/t/rpl_semi_sync_event.test

@@ -15,6 +15,7 @@ call mtr.add_suppression("Unsafe statement written to the binary log using state
 connection slave;
 call mtr.add_suppression("Master server does not support semi-sync");
 call mtr.add_suppression("Semi-sync slave .* reply");
+call mtr.add_suppression("Slave SQL.*Request to stop slave SQL Thread received while applying a group that has non-transactional changes; waiting for completion of the group");
 enable_query_log;
 
 connection master;