Bump third_party/pigweed/repo from f4d0b35 to cf4291d

Bumps [third_party/pigweed/repo](https://github.com/google/pigweed) from `f4d0b35` to `cf4291d`.
- [Commits](google/pigweed@f4d0b35...cf4291d)

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

Signed-off-by: dependabot[bot] <[email protected]>