Revert "Use Codex styles for buttons in language overlay"

This reverts commit d29050d080.

Reason for revert: I had mistakenly assumed the @wikimedia/codex
module was loaded on clicking the language button. It appears to
be added on page load.

Given T248718 it's still unclear what our policy on loading
@wikimedia/codex on page load is and given several people are out
I think it would be better to attempt this again next week, possibly
delaying further if needed.

Bug: T353071
Bug: T248718
Change-Id: I09334a1faec06a7400e61013ddda374156bf5d72

resources/js/ext.uls.interface.js

@@ -121,14 +121,7 @@
 	 * @return {jQuery}
 	 */
 	function createMenuButton( buttonClass ) {
-		// cdx-button--type-quiet is needed for 1.39 support.
-		// Please remove when support is no longer needed.
-		var classes = [
-			'cdx-button',
-			'cdx-button--weight-quiet',
-			'cdx-button--type-quiet',
-			buttonClass
-		];
+		var classes = [ 'mw-ui-button', 'mw-ui-quiet', buttonClass ];
 		// eslint-disable-next-line mediawiki/class-doc
 		return $( '<button>' ).addClass( classes );
 	}
@@ -587,7 +580,7 @@
 
 		ev.preventDefault();
 
-		mw.loader.using( [ 'ext.uls.mediawiki', '@wikimedia/codex' ] ).then( function () {
+		mw.loader.using( [ 'ext.uls.mediawiki', 'mediawiki.ui.button' ] ).then( function () {
 			var parent, languageNodes, standalone, uls;
 
 			parent = document.querySelectorAll( '.mw-portlet-lang, #p-lang' )[ 0 ];