Bump third_party/openthread/repo from 2aeb8b8 to ef8f170

Bumps [third_party/openthread/repo](https://github.com/openthread/openthread) from `2aeb8b8` to `ef8f170`.
- [Release notes](https://github.com/openthread/openthread/releases)
- [Commits](openthread/openthread@2aeb8b8...ef8f170)

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

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