[web] Fix several raw html flags in twig (#4325)

* [Update, Config] Add subject for watchdog emails

* [Web] Fixed sender_acl_disabled var in twig

* [Web] Fixed add_relayhost_hint var in twig

* [Web] Fixed merged_vars_hint var in twig

Co-authored-by: Valentin <vbrandner.itsb-b2018@fh-salzburg.ac.at>
Co-authored-by: Valentin <git@voidl.de>

data/web/templates/admin/tab-routing.twig

@@ -20,7 +20,7 @@
         </div>
       </div>
       <legend>{{ lang.admin.add_relayhost }}</legend>
-      <p class="help-block">{{ lang.admin.add_relayhost_hint }}</p>
+      <p class="help-block">{{ lang.admin.add_relayhost_hint|raw }}</p>
       <div class="row">
         <div class="col-md-8">
           <form class="form" data-id="rlyhost" role="form" method="post">