Bump third_party/prjxray from `a0c2d37` to `931576a`
Bump third_party/prjxray from `a0c2d37` to `931576a`

Bumps [third_party/prjxray](https://github.com/SymbiFlow/prjxray) from `a0c2d37` to `931576a`.
- [Release notes](https://github.com/SymbiFlow/prjxray/releases)
- [Commits](https://github.com/SymbiFlow/prjxray/compare/a0c2d372941f31ffde566ae0adc73d78cf46853a...931576a770a6dec5ca91c8d3368be59a98c19817)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
SymbiFlow/symbiflow-arch-defs,SymbiFlow/symbiflow-arch-defs