(follow-up) Fix "file not found" error in mediawiki.language.

* Follows-up f47dfe9939f7929f1e3fd1c501539cbd0d12373f, which forgot
  to remove the deleted files from the module definition as well.

exception 'MWException' with message 'ResourceLoaderFileModule::readScriptFiles: script file not found: "~/Development/mediawiki/core/resources/mediawiki.language/languages/nl.js"' in ~/Development/mediawiki/core/includes/resourceloader/ResourceLoaderFileModule.php:564
Stack trace:

Change-Id: Ib40d09071ba315da6b17fc94cca5746ed4c26342