Bump third_party/pigweed/repo from ead209d to 39f7220 (#24226)

Bumps [third_party/pigweed/repo](https://github.com/google/pigweed) from `ead209d` to `39f7220`.
- [Release notes](https://github.com/google/pigweed/releases)
- [Commits](google/pigweed@ead209d...39f7220)

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

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