Use namespaced MediaWiki\Extension\CLDR\LanguageNames

This change requires change I591628b98d16bfeecd32d157abc263be1036a71b
in extension cldr included in REL1_39 and above.

Change-Id: I6789961e4140e57e5f253fd2fbaeacf9860923e1

data/LanguageNameIndexer.php

@@ -24,6 +24,7 @@ if ( $IP === false ) {
 }
 require_once "$IP/maintenance/Maintenance.php";
 
+use MediaWiki\Extension\CLDR\LanguageNames;
 use MediaWiki\Languages\LanguageNameUtils;
 use MediaWiki\MediaWikiServices;