submodule: bump openthread from be7d36e to 4c96151 (#725)

Bumps [openthread](https://github.com/openthread/openthread) from `be7d36e` to `4c96151`.
- [Commits](openthread/openthread@be7d36e...4c96151)

---
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>

Author: dependabot[bot]