submodule: bump openthread from `87e6cf5` to `afa427b` (#56)
submodule: bump openthread from `87e6cf5` to `afa427b` (#56)

Bumps [openthread](https://github.com/openthread/openthread) from `87e6cf5` to `afa427b`.
- [Commits](https://github.com/openthread/openthread/compare/87e6cf59913a9b247086a81f3d4c58205bc34725...afa427b7f619be6e345595209b30e39eba927994)

---
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-kw41z,openthread/ot-kw41z