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
...

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