next.js

5eec6df5 - [metadata] disable streaming metadata for ppr deployment (#75978)

[metadata] disable streaming metadata for ppr deployment (#75978) ### What This PR forcedly disables the streaming metadata on vercel deployment when PPR is enabled on the target route. There're still some work need to be done on infra side, so we only let non-PPR mode and self-hosting PPR (mostly local testing) be controlled by `streamingMetadata` flag. Once the blocker is gone, then we can re-enable it