Bump third_party/openthread/repo from 837c7fd to a05954b

Bumps [third_party/openthread/repo](https://github.com/openthread/openthread) from `837c7fd` to `a05954b`.
- [Release notes](https://github.com/openthread/openthread/releases)
- [Commits](openthread/openthread@837c7fd...a05954b)

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

Signed-off-by: dependabot[bot] <[email protected]>