submodule: bump openthread from d3608df to 79a3a26 (#369)

Bumps [openthread](https://github.com/openthread/openthread) from `d3608df` to `79a3a26`.
- [Commits](openthread/openthread@d3608df...79a3a26)

---
updated-dependencies:
- dependency-name: openthread
  dependency-type: direct:production
...

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