submodule: bump third_party/openthread/repo from c2d5265 to `1e3c4d…

…7` (#2640)

Bumps [third_party/openthread/repo](https://github.com/openthread/openthread) from `c2d5265` to `1e3c4d7`.
- [Commits](openthread/openthread@c2d5265...1e3c4d7)

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

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