Bump third_party/pigweed/repo from e35aa3a to c8c31a0 (#30924)

Bumps [third_party/pigweed/repo](https://github.com/google/pigweed) from `e35aa3a` to `c8c31a0`.
- [Commits](google/pigweed@e35aa3a...c8c31a0)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>