Extension: react-router bundles its dev build into prod

[GabenGar]

It was raised in its repo already and the resolution is to wait for fix upstream because it's temporary.
The bundles are pretty big though, they take up 60% of each related entry, so I guess until they resolve their deps problem it's a revert to 6.28. The routers inside extension pages are client-only anyway and they don't use any fancy v7 features so it shouldn't be hard to do.

[GabenGar]

Turns out even the old version includes remix router of similar size, so the bundle size is the same.