fix: Upgrade portable-pty to resolve RUSTSEC-2017-0008 (#11732)
## Summary
- Upgrades `portable-pty` from 0.8.1 to 0.9.0, which replaces the
unmaintained `serial` crate with `serial2`
- No source code changes needed — the 0.9.0 API is fully compatible
Resolves TURBO-5252