submodule: bump openthread from f232204 to a2f000d

Bumps [openthread](https://github.com/openthread/openthread) from `f232204` to `a2f000d`.
- [Release notes](https://github.com/openthread/openthread/releases)
- [Commits](openthread/openthread@f232204...a2f000d)

---
updated-dependencies:
- dependency-name: openthread
  dependency-version: a2f000ddf80f66c3d9f9ac268d84e34d675f5bb1
  dependency-type: direct:production
...

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

Author: dependabot[bot]