Increase timeout in 021_row_visibility.pl.
Commit figured 30 seconds is long enough for anybody,
but in contexts like valgrind runs, it isn't necessarily.
@@ -33,7 +33,7 @@ $node_standby->start;
# instance being driven by us, add a timeout high enough that it
# should never trigger even on very slow machines, unless something
# is really wrong.
-my $psql_timeout = IPC::Run::timer(30);
+my $psql_timeout = IPC::Run::timer(300);
# One psql to primary and standby each, for all queries. That allows
# to check uncommitted changes being replicated and such.
