fix(next-core): fix determining dynamic route (#57435)
### What
Fixes how to determine if given route is dynamic to match next-dev does:
https://github.com/vercel/next.js/blob/462b8585b61b83fa079f40e2d8432cc643bf0713/packages/next/src/lib/metadata/get-metadata-route.ts#L79
We were passing calculated route instead to check if it's dynamic, so
`/sitemap` always considered as static since calculated route is
`/sitemap.xml`.
Closes WEB-1864
Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>
