Bump third_party/pigweed/repo from d6b036c to 7c87569

Bumps [third_party/pigweed/repo](https://github.com/google/pigweed) from `d6b036c` to `7c87569`.
- [Commits](google/pigweed@d6b036c...7c87569)

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

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