Make Perl warnings fatal in newly added TAP tests

New TAP tests added by commits 9a17be1e and 4710b67d missed to convert
warnings to FATAL.  This commit fixes that.

Author: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>

contrib/pg_stat_statements/t/010_restart.pl

@@ -4,7 +4,7 @@
 # across restarts.
 
 use strict;
-use warnings;
+use warnings FATAL => 'all';
 use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
 use Test::More;

src/bin/pg_upgrade/t/004_subscription.pl

@@ -2,7 +2,7 @@
 
 # Test for pg_upgrade of logical subscription
 use strict;
-use warnings;
+use warnings FATAL => 'all';
 
 use File::Find qw(find);