submodule: bump openthread from ffe2f52 to 905a22e (#794)

Bumps [openthread](https://github.com/openthread/openthread) from `ffe2f52` to `905a22e`.
- [Commits](openthread/openthread@ffe2f52...905a22e)

---
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>