Bump third_party/pigweed/repo from 71ba37c to 86bcb34

Bumps [third_party/pigweed/repo](https://github.com/google/pigweed) from `71ba37c` to `86bcb34`.
- [Release notes](https://github.com/google/pigweed/releases)
- [Commits](google/pigweed@71ba37c...86bcb34)

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

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