Bump third_party/ot-br-posix/repo from 23149c3 to 6d70f5e (project-chip#37840)

Bumps [third_party/ot-br-posix/repo](https://github.com/openthread/ot-br-posix) from `23149c3` to `6d70f5e`.
- [Release notes](https://github.com/openthread/ot-br-posix/releases)
- [Commits](openthread/ot-br-posix@23149c3...6d70f5e)

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

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Author: dependabot[bot]