Remove !defined( 'MEDIAWIKI' )

This may be causing a problem for the translate extension using
composer.json to run php code sniffer.

And not needed since we use extension.json if we use mediawiki 1.25+.

I traced back to the extension since translate extension in composer
requires this extension and seems to have that message.

Change-Id: I6c119c8f4744623e8756ce8da1869dfd66a3c026

UniversalLanguageSelector.php

@@ -30,10 +30,6 @@ if ( function_exists( 'wfLoadExtension' ) ) {
 	return;
 }
 
-if ( !defined( 'MEDIAWIKI' ) ) {
-	echo "This file is an extension to the MediaWiki software and cannot be used standalone.\n";
-	die( -1 );
-}
 /**
  * Version number used in extension credits and in other placed where needed.
  */