Fix regression in test_langs.php

Commit 78cee358 added file Web.config to plugins and lang folder.
test_langs.php treated the file as a plugin folder and a language file.
Merge branch 'fix13-test_langs' of github.com:atrol/mantisbt into atrol-fix13-test_langs
Fix #17510: regression in test_langs.php
remove legacy comment:

This was previously identified in c1945f2917726e62051a897676baefd32f2656e3