Use load balancer configuration, not load balancer id, in job-based LB removal logic

This is required to support RCv3.
I'm inclined to agree that the optimization argument is a red herring. What matters is making the code work, and it appears the arguments there are in favor of singular `remove_from_load_balancer`.

Conclusion from discussion on Slack with @cyli: we're probably going to remove it in a following PR. Removing it now is definitely work now; it won't be harder to remove later. OTOH, if we're wrong, and we do really want the bulk request for some reason, that means digging back into the source to recover this code. Furthermore, this has the cool side effect of not passing any RCv3 requests yet, which are not yet fully supported by underlying functions.