submodule: bump third_party/openthread/repo from 74573b5 to `1fceb2…

…2` (#2281)

Bumps [third_party/openthread/repo](https://github.com/openthread/openthread) from `74573b5` to `1fceb22`.
- [Commits](openthread/openthread@74573b5...1fceb22)

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

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