submodule: bump third_party/openthread/repo from b7006ce to `7344d9…

…c` (#890)

Bumps [third_party/openthread/repo](https://github.com/openthread/openthread) from `b7006ce` to `7344d9c`.
- [Commits](openthread/openthread@b7006ce...7344d9c)

---
updated-dependencies:
- dependency-name: third_party/openthread/repo
  dependency-type: direct:production
...

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