Change composer highlight border size to be more noticeable (#25010)

app/javascript/styles/mastodon/components.scss

@@ -3118,7 +3118,7 @@ $ui-header-height: 55px;
 
   &.active {
     transition: none;
-    box-shadow: 0 0 0 2px rgba(lighten($highlight-text-color, 8%), 0.7);
+    box-shadow: 0 0 0 6px rgba(lighten($highlight-text-color, 8%), 0.7);
   }
 }