submodule: bump openthread from 944a246 to bd310db

Bumps [openthread](https://github.com/openthread/openthread) from `944a246` to `bd310db`.
- [Release notes](https://github.com/openthread/openthread/releases)
- [Commits](openthread/openthread@944a246...bd310db)

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

Signed-off-by: dependabot[bot] <[email protected]>