Don't run rowsecurity in parallel with other regression tests.

The short-lived event trigger in the rowsecurity test causes irreproducible
failures when the concurrent tests do something that the event trigger
can't cope with.  Per buildfarm.

src/test/regress/parallel_schedule

@@ -78,12 +78,15 @@ ignore: random
 # ----------
 # Another group of parallel tests
 # ----------
-test: select_into select_distinct select_distinct_on select_implicit select_having subselect union case join aggregates transactions random portals arrays btree_index hash_index update namespace prepared_xacts delete
+test: select_into select_distinct select_distinct_on select_implicit select_having subselect union case join aggregates transactions random portals arrays btree_index hash_index update delete namespace prepared_xacts
 
 # ----------
 # Another group of parallel tests
 # ----------
-test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address
+test: brin gin gist spgist privileges security_label collate matview lock replica_identity object_address
+
+# rowsecurity creates an event trigger, so don't run it in parallel
+test: rowsecurity
 
 # ----------
 # Another group of parallel tests

src/test/regress/serial_schedule

@@ -105,8 +105,8 @@ test: collate
 test: matview
 test: lock
 test: replica_identity
-test: rowsecurity
 test: object_address
+test: rowsecurity
 test: alter_generic
 test: misc
 test: psql