submodule: bump third_party/openthread/repo from `925b12c` to `b6ac79f` (#1481)
submodule: bump third_party/openthread/repo from `925b12c` to `b6ac79f` (#1481)

Bumps [third_party/openthread/repo](https://github.com/openthread/openthread) from `925b12c` to `b6ac79f`.
- [Commits](https://github.com/openthread/openthread/compare/925b12cc083b51e0c3366ef5e5e01a09c6434e32...b6ac79f61a6a7c4a93030db34b3398d066d8182a)

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

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>

Co-authored-by: dependabot[bot] <1c358da00a777d4e9898c1280ab801e2df165188@users.noreply.github.com>
openthread/ot-br-posix,openthread/borderrouter,openthread/borderrouter,openthread/borderrouter,openthread/ot-br-posix,openthread/borderrouter,openthread/ot-br-posix,openthread/borderrouter,openthread/ot-br-posix,openthread/borderrouter,openthread/ot-br-posix,openthread/ot-br-posix