Refactor clone-panel styles (#29861)

1. The borders were doubled on the "empty" page, fix it.
2. Remove unnecessary CSS classes like "clone", "compact", etc
3. Use CSS class "clone-panel" instead of ID "clone-panel"
4. Use `tw-flex-1` instead of `gt-f1`
5. Remove unnecessary ID "more-btn"

web_src/css/repo/wiki.css

@@ -58,7 +58,7 @@
 }
 
 @media (max-width: 767.98px) {
-  .repository.wiki #clone-panel #repo-clone-url {
+  .repository.wiki .clone-panel #repo-clone-url {
     width: 160px;
   }
   .repository.wiki .wiki-content-main.with-sidebar,