submodule: bump openthread from `7dd7a5d` to `3f40cf7` (#86)
submodule: bump openthread from `7dd7a5d` to `3f40cf7` (#86)

Bumps [openthread](https://github.com/openthread/openthread) from `7dd7a5d` to `3f40cf7`.
- [Commits](https://github.com/openthread/openthread/compare/7dd7a5d7d682505826031dca018560615e0a8789...3f40cf78e61215f8841877ab7327d06e47485e55)

---
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-b91,openthread/ot-b91