The migration was first made in 1.16.0-alpha.1, so that means 2 releases have been out that set the replicas to zero.
This removal negatively impacts anyone that created a cluster from kops HEAD between 1.15.0 and 1.16.0-alpha.1, and then upgraded kops directly to the 1.16.0 release that includes this commit, without having first upgraded to either of the alphas.

That seems like a reasonably small enough audience that this is safe to remove now.
Perhaps we mention in the release notes that anyone using HEAD or one of the alpha releases needs to `kubectl delete -n kube-system deployment kops-controller`