Waiting list: Add additional explanation (Z#23157006)

src/pretix/presale/templates/pretixpresale/event/waitinglist.html

@@ -34,6 +34,11 @@
                             {% endblocktrans %}
                         {% endif %}
                     </p>
+                    <p class="help-block">
+                        {% blocktrans trimmed %}
+                            You will <strong>not</strong> receive a confirmation email after you have been added to the waiting list. We will only contact you once a spot opens up.
+                        {% endblocktrans %}
+                    </p>
                     <p>
                         <button type="submit" class="btn btn-primary">
                             {% trans "Add me to the list" %}