Use LanguageNameUtils::AUTONYMS/SUPPORTED instead of hard coded value

Easier to spot the documentation what happen with this option

Change-Id: I977485c2cba0063b5bdee3724d9262b75341faec

data/LanguageNameSearch.php

@@ -1,5 +1,6 @@
 <?php
 
+use MediaWiki\Languages\LanguageNameUtils;
 use MediaWiki\MediaWikiServices;
 
 /**
@@ -82,7 +83,7 @@ class LanguageNameSearch {
 				// If $userLanguage is not provided (null), it is the same as autonym
 				$candidates = [
 					mb_strtolower( $languageNameUtils->getLanguageName( $code, $userLanguage ) ),
-					mb_strtolower( $languageNameUtils->getLanguageName( $code, null ) ),
+					mb_strtolower( $languageNameUtils->getLanguageName( $code, LanguageNameUtils::AUTONYMS ) ),
 					$name
 				];
 

includes/Hooks.php

@@ -270,7 +270,8 @@ class Hooks implements
 	 * @return string
 	 */
 	protected function getDefaultLanguage( array $preferred ) {
-		$supported = $this->languageNameUtils->getLanguageNames( LanguageNameUtils::AUTONYMS, 'mwfile' );
+		$supported = $this->languageNameUtils
+			->getLanguageNames( LanguageNameUtils::AUTONYMS, LanguageNameUtils::SUPPORTED );
 
 		// look for a language that is acceptable to the client
 		// and known to the wiki.