update menu bar active nav path detection

src/app/layout/Menu.svelte

@@ -66,11 +66,6 @@
   });
 
   onMount(() => {
-    updateActiveNavPath();
-    // the mutation observer callback runs too fast, hence the call to `updateActiveNavPath` must be wrapped in an empty
-    // setTimeout to not cause any visual bugs
-    new MutationObserver(() => setTimeout(updateActiveNavPath)).observe(document.head, { childList: true });
-
     document.addEventListener('astro:page-load', () => {
       pageLoadTimestamp = Date.now();
 
@@ -88,6 +83,8 @@
 
       document.body.addEventListener('touchstart', touchStartListener);
       document.body.addEventListener('touchend', touchEndListener);
+
+      updateActiveNavPath();
     });
   });