Revert "dx: avoid next-env.d.ts change in dev" (#88153)
Reverting since it produced merge conflicts with in-progress
[strict-route-types
project](https://linear.app/vercel/project/nextjs-strict-route-types-2f0a70110d5d/overview):
The lesson learned from the earlier PR was that this is a risky change.
We'll land a similar change flagged in
https://github.com/vercel/next.js/pull/87768
