Document orchestrator go-livepeer voting behaviour

[rickstaa]

The ability to vote via the go-livepeer client was added in [PR #3275](https://github.com/livepeer/go-livepeer/pull/3275). Update the docs to clarify that orchestrators can vote directly using the go-livepeer CLI.This note will help operators understand that they don’t need to import their wallet into a browser, providing a more secure governance workflow.