Bump third_party/openthread/repo from f0b6fce to d015004

Bumps [third_party/openthread/repo](https://github.com/openthread/openthread) from `f0b6fce` to `d015004`.
- [Release notes](https://github.com/openthread/openthread/releases)
- [Commits](openthread/openthread@f0b6fce...d015004)

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

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