chore: bump pnpm to 9.6.0 (#68044)
## Why?
- More support for [catalogs](https://pnpm.io/catalogs) (read
[changelog](https://github.com/pnpm/pnpm/releases) for more info).
- Successful
[build-and-deploy](https://github.com/vercel/next.js/actions/runs/10127840891)
run
