submodule: bump openthread from ae5832f to 459a4cb (#1155)

Bumps [openthread](https://github.com/openthread/openthread) from `ae5832f` to `459a4cb`.
- [Commits](openthread/openthread@ae5832f...459a4cb)

---
updated-dependencies:
- dependency-name: openthread
  dependency-version: 459a4cbb88c57db76397f67e534a3b7388368b60
  dependency-type: direct:production
...

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Author: dependabot[bot]