submodule: bump third_party/openthread/repo from 97a3f76 to `d7810f…

…a` (#2493)

Bumps [third_party/openthread/repo](https://github.com/openthread/openthread) from `97a3f76` to `d7810fa`.
- [Commits](openthread/openthread@97a3f76...d7810fa)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>