CSS codemod: ensure we don't lose selectors

[RobinMalfait]

This PR fixes an issue where a CSS rule with a selector that contains multiple selectors lost everything but the last selector.

While testing the npx @tailwindcss/upgrade codemods on real world projects, I noticed that we lost one of the selectors in the docker/docs repository.

diff --git a/assets/css/toc.css b/assets/css/toc.css
index 91ff92d7cd..3b2432e913 100644
--- a/assets/css/toc.css
+++ b/assets/css/toc.css
@@ -2,7 +2,7 @@
   #TableOfContents {
     .toc a {
       @apply block max-w-full truncate py-1 pl-2 hover:font-medium hover:no-underline;
-      &[aria-current="true"],
+      
       &:hover {
         @apply border-l-2 border-l-gray-light bg-gradient-to-r from-gray-light-100 font-medium text-black dark:border-l-gray-dark dark:from-gray-dark-200 dark:text-white;
       }

This PR fixes the issue by not overriding the node.selector internally with the last selector we handled. Instead, we let the selector parser handle it entirely.