submodule: bump openthread from 830572f to 0c6c2fe

Bumps [openthread](https://github.com/openthread/openthread) from `830572f` to `0c6c2fe`.
- [Release notes](https://github.com/openthread/openthread/releases)
- [Commits](openthread/openthread@830572f...0c6c2fe)

---
updated-dependencies:
- dependency-name: openthread
  dependency-type: direct:production
...

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