perlcritic: make all open() calls three-argument

Two-argument calls end up parsing the second argument to guess what
should happen, three-arg parses ... less?

t/plugins/gitea.t

@@ -60,7 +60,7 @@ if (!defined($pid = fork())) {
     kill('INT', $pid);
 }
 
-open my $fh, $filename or die ("Can't open(): $!\n");
+open(my $fh, "<", $filename) or die ("Can't open(): $!\n");
 my $i = 0;
 my $uri = <$fh>;
 my $data = <$fh>;