submodule: bump openthread from b0e7b14 to 696c709

Bumps [openthread](https://github.com/openthread/openthread) from `b0e7b14` to `696c709`.
- [Release notes](https://github.com/openthread/openthread/releases)
- [Commits](openthread/openthread@b0e7b14...696c709)

---
updated-dependencies:
- dependency-name: openthread
  dependency-version: 696c70994cbaf318f3943a9e93f066952ab6b9ec
  dependency-type: direct:production
...

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

Author: dependabot[bot]