Fix one of the tests introduced in commit 52e4f0c.

In the Publisher-Subscriber setup, after performing a DML operation on the
publisher, we need to wait for it to be replayed on the subscriber before
querying the same data on the subscriber. One of the tests missed the wait
step.

As per buildfarm.

Author: Peter Smith
Discussion: https://postgr.es/m/CAHut+Pv=e9Qd1TSYo8Og6x6Abfz3b9_htwinLp4ENPgV45DACQ@mail.gmail.com

Author: Amit Kapila

src/test/subscription/t/028_row_filter.pl

@@ -677,6 +677,8 @@
 $node_publisher->safe_psql('postgres',
 	"UPDATE tab_rowfilter_toast SET b = '1'");
 
+$node_publisher->wait_for_catchup($appname);
+
 # Check expected replicated rows for tab_rowfilter_toast
 # tab_rowfilter_toast filter: (a = repeat('1234567890', 200) AND b < '10')
 # UPDATE old  (repeat('1234567890', 200) ,'1234567890')  NO