Bump third_party/pigweed/repo from 1f12d06 to 8512b20

Bumps [third_party/pigweed/repo](https://github.com/google/pigweed) from `1f12d06` to `8512b20`.
- [Commits](google/pigweed@1f12d06...8512b20)

---
updated-dependencies:
- dependency-name: third_party/pigweed/repo
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>