Bump third_party/nanopb/repo from 423c03b to f8724ee (#31735)

Bumps [third_party/nanopb/repo](https://github.com/nanopb/nanopb) from `423c03b` to `f8724ee`.
- [Commits](nanopb/nanopb@423c03b...f8724ee)

---
updated-dependencies:
- dependency-name: third_party/nanopb/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>