submodule: bump openthread from e4d953c to 4ae6914 (#514)

Bumps [openthread](https://github.com/openthread/openthread) from `e4d953c` to `4ae6914`.
- [Commits](openthread/openthread@e4d953c...4ae6914)

---
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>