submodule: bump openthread from `6809b33` to `390efb4` (#314)
submodule: bump openthread from `6809b33` to `390efb4` (#314)

Bumps [openthread](https://github.com/openthread/openthread) from `6809b33` to `390efb4`.
- [Commits](https://github.com/openthread/openthread/compare/6809b33f315d671f4333c389712b509b0bee8df3...390efb4c38a7a13ea798cd633c6a3aed05afc05b)

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

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>

Co-authored-by: dependabot[bot] <1c358da00a777d4e9898c1280ab801e2df165188@users.noreply.github.com>
openthread/ot-samr21,openthread/ot-samr21