build(deps): bump third_party/prjxray from `ff4c807` to `84e168c`
build(deps): bump third_party/prjxray from `ff4c807` to `84e168c`

Bumps [third_party/prjxray](https://github.com/SymbiFlow/prjxray) from `ff4c807` to `84e168c`.
- [Release notes](https://github.com/SymbiFlow/prjxray/releases)
- [Commits](https://github.com/SymbiFlow/prjxray/compare/ff4c80738d8527c09aa57ee1a0503c906e9d5252...84e168c9dcd41e71d010c74975f91632f978307c)
SymbiFlow/symbiflow-xc-fasm2bels