Bump third_party/ot-br-posix/repo from 9326cc3 to c5a7a35 (#32069)

Bumps [third_party/ot-br-posix/repo](https://github.com/openthread/ot-br-posix) from `9326cc3` to `c5a7a35`.
- [Release notes](https://github.com/openthread/ot-br-posix/releases)
- [Commits](openthread/ot-br-posix@9326cc3...c5a7a35)

---
updated-dependencies:
- dependency-name: third_party/ot-br-posix/repo
  dependency-type: direct:production
...

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