Bump third_party/nanopb/repo from 671672b to 8e9d5a1

Bumps [third_party/nanopb/repo](https://github.com/nanopb/nanopb) from `671672b` to `8e9d5a1`.
- [Commits](nanopb/nanopb@671672b...8e9d5a1)

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

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

third_party/nanopb/repo

@@ -0,0 +1 @@
+8e9d5a10125b596188e95e925937d380a3c79e8e