fix: remove extra endcall in calendar header template

The premature endcall closed menu_row before desktop_nav,
causing a Jinja nesting error.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/_types/calendar/header/_header.html

@@ -11,7 +11,6 @@
         {% from '_types/calendar/_description.html' import description %}
         {{description(calendar)}}
       </div>
-    {% endcall %}
     {% call links.desktop_nav() %}
       {% include '_types/calendar/_nav.html' %}
     {% endcall %}