submodule: bump openthread from 45c5fe4 to f9349c1 (#790)

Bumps [openthread](https://github.com/openthread/openthread) from `45c5fe4` to `f9349c1`.
- [Commits](openthread/openthread@45c5fe4...f9349c1)

---
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>