pg_amcheck: Keep trying to fix the tests.

Commit 24189277 managed to remove
one of the two places where we were checking for a "no such user"
error while leaving the other one right next to it. So remove that
too. In fact, remove the entire test, because the whole point of
this test was to see which message we got on a failure.

src/bin/pg_amcheck/t/002_nonesuch.pl

@@ -3,7 +3,7 @@ use warnings;
 
 use PostgresNode;
 use TestLib;
-use Test::More tests => 75;
+use Test::More tests => 72;
 
 # Test set-up
 my ($node, $port);
@@ -71,15 +71,6 @@ $node->command_checks_all(
 	[ ],
 	'checking with a non-existent user');
 
-# Failing to connect to the initial database due to bad username is an still an
-# error under --no-strict-names.
-$node->command_checks_all(
-	[ 'pg_amcheck', '--no-strict-names', '-U', 'no_such_user', 'postgres' ],
-	1,
-	[ qr/^$/ ],
-	[ qr/role "no_such_user" does not exist/ ],
-	'checking with a non-existent user under --no-strict-names');
-
 #########################################
 # Test checking databases without amcheck installed