Update askama

crates/frontend/public/templates/pages/calendar.html

@@ -8,7 +8,7 @@
 <h1>{{ name }}</h1>
 {% if let Some(description) = calendar.description %}<p>{{ description }}</p>{% endif%}
 
-<pre>{{ calendar|yaml }}</pre>
+<pre>{{ calendar|json }}</pre>
 
 <a href="/frontend/user/{{ calendar.principal }}">Back</a>
 {% endblock %}