submodule: bump openthread from `61ecd90` to `e8b9b87` (#316)
submodule: bump openthread from `61ecd90` to `e8b9b87` (#316)

Bumps [openthread](https://github.com/openthread/openthread) from `61ecd90` to `e8b9b87`.
- [Commits](https://github.com/openthread/openthread/compare/61ecd9053158ef61b3afca75a8606e237f8cac8f...e8b9b874f51b74ce6339f3f963897aee0eb0879f)

---
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-efr32,openthread/ot-efr32,openthread/ot-efr32