plainui: properly disable themeswitcher (temporarily)

src/plainui/jinja2/plainui/base.html.j2

@@ -109,7 +109,7 @@
               <ul class="d-flex gap-2 list-unstyled">
                 <li>{{ hbtns.share() }}</li>
                 <!-- Temporary disabled due to 38c3 design implementation.
-                <li>{{ hbtns.themeswitcher() }}</li>
+                <li>{# hbtns.themeswitcher() #}</li>
                 -->
                 <li>{{ hbtns.globe() }}</li>
               </ul>