Bump third_party/pigweed/repo from e765c4d to 9504c03 (#29821)

Bumps [third_party/pigweed/repo](https://github.com/google/pigweed) from `e765c4d` to `9504c03`.
- [Commits](google/pigweed@e765c4d...9504c03)

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

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