submodule: bump openthread from 43cc05a to 85afd12 (#1158)

Bumps [openthread](https://github.com/openthread/openthread) from `43cc05a` to `85afd12`.
- [Commits](openthread/openthread@43cc05a...85afd12)

---
updated-dependencies:
- dependency-name: openthread
  dependency-version: 85afd129a64314b2e338272788ea54fa6726d779
  dependency-type: direct:production
...

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Author: dependabot[bot]