submodule: bump third_party/openthread/repo from 7048835 to 494575f (#3362)

Bumps [third_party/openthread/repo](https://github.com/openthread/openthread) from `7048835` to `494575f`.
- [Commits](openthread/openthread@7048835...494575f)

---
updated-dependencies:
- dependency-name: third_party/openthread/repo
  dependency-version: 494575f8fc43c1d4cc293a1860ab3f5508e91293
  dependency-type: direct:production
...

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Author: dependabot[bot]