submodule: bump third_party/openthread/repo from c10f650 to 6009dec

Bumps [third_party/openthread/repo](https://github.com/openthread/openthread) from `c10f650` to `6009dec`.
- [Release notes](https://github.com/openthread/openthread/releases)
- [Commits](openthread/openthread@c10f650...6009dec)

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

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