Language alert box should use Html::noticeBox

Html::noticeBox doesn't output any deprecated classes so
will not conflict with any user gadgets now.

Bug: T299625
Change-Id: Ic9aef5c8ff3fae6a79c7cf82cc3c97714cf40b3d

includes/SkinVector.php

@@ -673,9 +673,9 @@ class SkinVector extends SkinMustache {
 			// T295555 Add language switch alert message temporarily (to be removed).
 			if ( $this->shouldLanguageAlertBeInSidebar() && !$parentData['is-mainpage'] ) {
 				$languageSwitchAlert = [
-					'html-content' => Html::rawElement( 'div',
-						[ 'class' => 'messagebox' ],
-						$this->msg( 'vector-language-redirect-to-top' )->parse()
+					'html-content' => Html::noticeBox(
+						$this->msg( 'vector-language-redirect-to-top' )->parse(),
+						'vector-language-sidebar-alert'
 					),
 				];
 				$headingOptions = [

resources/skins.vector.styles/components/Sidebar.less

@@ -38,7 +38,7 @@
 		}
 
 		// T295555 style overrides for temporary language switch alert (can be removed later ).
-		.messagebox {
+		.vector-language-sidebar-alert {
 			padding: 0.75em;
 		}
 	}