test: fix invalid URL in app-types test (#68360)
This PR fixes a test that typechecks, but crashes when actually running
the page, because
1. `new URL("/relative")` will throw (so we change it to absolute)
2. We cannot pass a URL object from RSC to a client component (so we
just make the page 'use client', which also requires removing
`metadata`, but that wasn't used for anything)
See https://github.com/vercel/next.js/pull/68323#discussion_r1698468251,
where this was split from
