fix(docs): stop redirecting /auth/quickstart away from its own index

The 302 to /auth/quickstart/react was a workaround for the folder having
no index page. It has one now, and the redirect shadowed it — the URL the
landing links to never rendered the overview.

Exactly the case the "TEMPORARY (302) on purpose" comment was written
for, so nothing is cached hard and this takes effect immediately.
check-links can't catch it: it crawls prerendered HTML and the page file
exists — the redirect only applies at request time.

Author: boyander

next.config.mjs

@@ -32,11 +32,8 @@ export default withNextra({
         destination: '/auth/guides/migrate-from-auth0',
         permanent: false
       },
-      {
-        source: '/auth/quickstart',
-        destination: '/auth/quickstart/react',
-        permanent: false
-      },
+      // NOTE: /auth/quickstart is NOT here — it has a real index page now, and
+      // a redirect would shadow it. This is why these are 302s.
       {
         source: '/auth/extensibility',
         destination: '/auth/extensibility/actions',