submodule: bump openthread from `687e04f` to `237c91b` (#235)
submodule: bump openthread from `687e04f` to `237c91b` (#235)

Bumps [openthread](https://github.com/openthread/openthread) from `687e04f` to `237c91b`.
- [Commits](https://github.com/openthread/openthread/compare/687e04f6d460ec48b7b5b88216ed4b6d7348b81c...237c91b9398bfe55426c45cbe5bcb5713c178ba3)

---
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-cc13x2-cc26x2,openthread/ot-cc13x2-cc26x2