Bump third_party/ot-br-posix/repo from 23149c3 to 6d70f5e

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
...

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

Author: dependabot[bot]

third_party/ot-br-posix/repo

@@ -0,0 +1 @@
+6d70f5e5738f65307aada17caad999c199a29ac3