submodule: bump openthread from 8bb5b30 to 5f03f0e (#1147)

Bumps [openthread](https://github.com/openthread/openthread) from `8bb5b30` to `5f03f0e`.
- [Commits](openthread/openthread@8bb5b30...5f03f0e)

---
updated-dependencies:
- dependency-name: openthread
  dependency-version: 5f03f0e14b510e1ca201f50021367975d44b76b8
  dependency-type: direct:production
...

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Author: dependabot[bot]