Make all Perl warnings fatal in 043_wal_replay_wait.pl

This file was committed after c538592, but accidentally missed changing
all warnings into fatal errors.

Reported-by: Anton Voloshin
Discussion: https://postgr.es/m/aa8a55d5-554a-4027-a491-1b0ca7c85f7a%40postgrespro.ru

Author: akorotkov

src/test/recovery/t/043_wal_replay_wait.pl

@@ -1,7 +1,7 @@
 # Checks waiting for the lsn replay on standby using
 # pg_wal_replay_wait() procedure.
 use strict;
-use warnings;
+use warnings FATAL => 'all';
 
 use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;