[BS5] add layout spacing

data/web/templates/admin/tab-config-quota.twig

@@ -4,7 +4,7 @@
     <div class="card-body">
       <p>{{ lang.admin.quota_notifications_info }}</p>
       <form class="form" role="form" data-id="quota_notification" method="post">
-        <div class="row">
+        <div class="row mb-4">
           <div class="col-sm-6">
             <div>
               <label for="quota_notification_sender">{{ lang.admin.quota_notification_sender }}:</label>