Bump third_party/pigweed/repo from 74144e6 to 81460c6 (project-ch…

…ip#20266)

Bumps [third_party/pigweed/repo](https://github.com/google/pigweed) from `74144e6` to `81460c6`.
- [Release notes](https://github.com/google/pigweed/releases)
- [Commits](google/pigweed@74144e6...81460c6)

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

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

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