submodule: bump openthread from `b4c76b3` to `19cd73d` (#165)
submodule: bump openthread from `b4c76b3` to `19cd73d` (#165)

Bumps [openthread](https://github.com/openthread/openthread) from `b4c76b3` to `19cd73d`.
- [Commits](https://github.com/openthread/openthread/compare/b4c76b3e170a729f9bdb57ddaa6d05b73e541ce2...19cd73d69121c33d8d65cb0c4524cc5aa9084bd0)

---
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-qorvo,openthread/ot-qorvo,openthread/ot-qorvo