submodule: bump openthread from 0f4fbab to 42635a1 (#1141)

Bumps [openthread](https://github.com/openthread/openthread) from `0f4fbab` to `42635a1`.
- [Commits](openthread/openthread@0f4fbab...42635a1)

---
updated-dependencies:
- dependency-name: openthread
  dependency-version: 42635a12b2624b7939131915dd0f50d7043b9761
  dependency-type: direct:production
...

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Author: dependabot[bot]