submodule: bump openthread from 0a74d66 to 4dddcb6 (#231)

Bumps [openthread](https://github.com/openthread/openthread) from `0a74d66` to `4dddcb6`.
- [Commits](openthread/openthread@0a74d66...4dddcb6)

---
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>