submodule: bump openthread from 7048835 to fa5bb3b (#1170)

Bumps [openthread](https://github.com/openthread/openthread) from `7048835` to `fa5bb3b`.
- [Commits](openthread/openthread@7048835...fa5bb3b)

---
updated-dependencies:
- dependency-name: openthread
  dependency-version: fa5bb3b94c01dbc5fc22f1a932b91be280f450d1
  dependency-type: direct:production
...

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