refactor: remove unused css for hr

src/components/Header.astro

@@ -99,9 +99,6 @@ const { activeNav } = Astro.props;
   #skip-to-content {
     @apply bg-skin-accent text-skin-inverted py-2 px-3 absolute -top-full focus:top-4 left-16 z-50 transition-all;
   }
-  header hr {
-    @apply border-skin-line mx-4 max-w-3xl sm:mx-auto;
-  }
   .nav-container {
     @apply max-w-3xl mx-auto flex flex-col sm:flex-row justify-between items-center;
   }