[BS5] change bootstrap general

data/web/templates/mailbox/tab-resources.twig

@@ -11,7 +11,7 @@
         </ul>
       </div>
     </div>
-    <div class="card-body help-block">
+    <div class="card-body text-muted">
       <p><span class="badge fs-5 bg-success">{{ lang.mailbox.booking_0_short }}</span> - {{ lang.mailbox.booking_null }}</p>
       <p><span class="badge fs-5 bg-warning">{{ lang.mailbox.booking_lt0_short }}</span> - {{ lang.mailbox.booking_ltnull }}</p>
       <p><span class="badge fs-5 bg-danger">{{ lang.mailbox.booking_custom_short }}</span> - {{ lang.mailbox.booking_custom }}</p>