Replace Language::getLanguageNames with TranslateUtils::getLanguageNames

To make sure that the appropriate supported language codes are loaded.

Found by Niklas when debugging the loading of qqq messages for
the core MediaWiki group on a test wiki.

Change-Id: Ie829843cb797806aa02aa6d994f900d039891b92
Merge "Replace Language::getLanguageNames with TranslateUtils::getLanguageNames"