### What
Change the metadataBase missing warning for all cases to only warn in
standalone mode or the non-vercel deployment.
### Why
In vercel deployments, previous concern was that you might not discover
you missed that metadataBase when you deploy. But now we have sth
fallback on production deployments. So we only need to warn in
non-vercel deployment.
Standalone is usually for self-hoist, we always warn users to set the
`metadataBase` to make sure the domain can be properly resolved.
[x-ref](https://vercel.slack.com/archives/C03S8ED1DKM/p1716926825853389?thread_ts=1716923373.484329&cid=C03S8ED1DKM)
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