Bump third_party/nanopb/repo from cf26d28 to 423c03b (#31421)

Bumps [third_party/nanopb/repo](https://github.com/nanopb/nanopb) from `cf26d28` to `423c03b`.
- [Commits](nanopb/nanopb@cf26d28...423c03b)

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

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