Adding escapeHtml to Newsletter phtml

Author: rafaelstz

app/code/Magento/Newsletter/view/frontend/templates/subscribe.phtml

@@ -10,7 +10,7 @@
 
 ?>
 <div class="block newsletter">
-    <div class="title"><strong><?php /* @escapeNotVerified */ echo __('Newsletter') ?></strong></div>
+    <div class="title"><strong><?php echo $block->escapeHtml(__('Newsletter')) ?></strong></div>
     <div class="content">
         <form class="form subscribe"
             novalidate