typo

mail/layouts/html.php

@@ -2,7 +2,7 @@
 use yii\helpers\Html;
 
 /* @var $this \yii\web\View view component instance */
-/* @var $message \yii\mail\MessageInterface the message bing composed */
+/* @var $message \yii\mail\MessageInterface the message being composed */
 /* @var $content string main view render result */
 ?>
 <?php $this->beginPage() ?>