Remove TAP test for createdb --lc-ctype

OpenBSD falls back to "C" when using an incorrect input with setlocale()
and LC_CTYPE, causing this test, introduced by 008cf040, to fail.  This
removes the culprit test to avoid the portability issue.

Per report from Robert Haas, via buildfarm member curculio.

Discussion: https://postgr.es/m/CA+TgmoZ6ddh3mHD9gU8DvNYoFmuJaYYn1+4AvZNp25vTdRwCAQ@mail.gmail.com
Backpatch-through: 11

src/bin/scripts/t/020_createdb.pl

@@ -3,7 +3,7 @@ use warnings;
 
 use PostgresNode;
 use TestLib;
-use Test::More tests => 22;
+use Test::More tests => 19;
 
 program_help_ok('createdb');
 program_version_ok('createdb');
@@ -40,11 +40,3 @@ $node->command_checks_all(
 		qr/^createdb: error: database creation failed: ERROR:  invalid locale name/s
 	],
 	'createdb with incorrect --lc-collate');
-$node->command_checks_all(
-	[ 'createdb', '--lc-ctype', "foo'; SELECT '1", 'foobar2' ],
-	1,
-	[qr/^$/],
-	[
-		qr/^createdb: error: database creation failed: ERROR:  invalid locale name/s
-	],
-	'createdb with incorrect --lc-ctype');