Bump third_party/ot-br-posix/repo from 636e53d to 69ce2a5 (#29904)

Bumps [third_party/ot-br-posix/repo](https://github.com/openthread/ot-br-posix) from `636e53d` to `69ce2a5`.
- [Release notes](https://github.com/openthread/ot-br-posix/releases)
- [Commits](openthread/ot-br-posix@636e53d...69ce2a5)

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

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