submodule: bump third_party/openthread/repo from 2cc0798 to `709692…

…8` (#2405)

Bumps [third_party/openthread/repo](https://github.com/openthread/openthread) from `2cc0798` to `7096928`.
- [Commits](openthread/openthread@2cc0798...7096928)

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

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