Revert recent changes to 002_pg_upgrade.pl.

The test is proving to be unreliable in the buildfarm, and we neither
agree on how best to fix it nor have time to do so before the upcoming
release. So for now, put things back to the way they were before commit
d498e052b4.

Discussion: http://postgr.es/m/3628089.1659640252@sss.pgh.pa.us

src/bin/pg_upgrade/t/002_pg_upgrade.pl

@@ -208,25 +208,6 @@ if (defined($ENV{oldinstall}))
 	}
 }
 
-$oldnode->safe_psql("regression", "VACUUM FULL pg_largeobject;");
-
-# Record the relfrozenxid and relminmxid horizons from the old server.
-my $horizon_query = <<EOM;
-SELECT
-  c.oid::regclass, c.relfrozenxid, c.relminmxid
-FROM
-  pg_class c, pg_namespace n
-WHERE
-  c.relnamespace = n.oid AND
-  ((n.nspname !~ '^pg_temp_' AND n.nspname !~ '^pg_toast_temp_' AND
-    n.nspname NOT IN ('pg_catalog', 'information_schema', 'binary_upgrade',
-                      'pg_toast'))
-  OR (n.nspname = 'pg_catalog' AND relname IN ('pg_largeobject')))
-ORDER BY c.oid::regclass::text
-EOM
-$horizon_query =~ s/\s+/ /g; # run it together on one line
-my $horizon1 = $oldnode->safe_psql('regression', $horizon_query);
-
 # In a VPATH build, we'll be started in the source directory, but we want
 # to run pg_upgrade in the build directory so that any files generated finish
 # in it, like delete_old_cluster.{sh,bat}.
@@ -311,9 +292,6 @@ $newnode->command_ok(
 	],
 	'dump after running pg_upgrade');
 
-# And record the horizons from the upgraded cluster as well.
-my $horizon2 = $newnode->safe_psql('regression', $horizon_query);
-
 # Compare the two dumps, there should be no differences.
 my $compare_res = compare("$tempdir/dump1.sql", "$tempdir/dump2.sql");
 is($compare_res, 0, 'old and new dumps match after pg_upgrade');
@@ -331,28 +309,4 @@ if ($compare_res != 0)
 	print "=== EOF ===\n";
 }
 
-# Compare the horizons, there should be no differences.
-my $horizons_ok = $horizon1 eq $horizon2;
-ok($horizons_ok, 'old and new horizons match after pg_upgrade');
-
-# Provide more context if the horizons do not match.
-if (! $horizons_ok)
-{
-	# output is long, so use diff to compare
-	open my $fh, ">", "$tempdir/horizon1.txt" or die "could not open file: $!";
-	print $fh $horizon1;
-	close $fh;
-	open $fh, ">", "$tempdir/horizon2.txt" or die "could not open file: $!";
-	print $fh $horizon2;
-	my ($stdout, $stderr) =
-		run_command([ 'diff', "$tempdir/horizon1.txt", "$tempdir/horizon2.txt" ]);
-	close $fh;
-	print "=== diff of $tempdir/horizon1.txt and $tempdir/horizon2.txt\n";
-	print "=== stdout ===\n";
-	print $stdout;
-	print "=== stderr ===\n";
-	print $stderr;
-	print "=== EOF ===\n";
-}
-
 done_testing();