Change contrast of status links that are not mentions nor hashtags (#11406)

app/javascript/styles/mastodon/components.scss

@@ -753,6 +753,10 @@
     }
   }
 
+  a.unhandled-link {
+    color: lighten($ui-highlight-color, 8%);
+  }
+
   .status__content__spoiler-link {
     background: $action-button-color;