Reflector metrics are not available

[skonto]

Expected Behavior

See reflector metrics exported

Actual Behavior

No reflector metrics are exported

Steps to Reproduce the Problem

1. Installed v0.19.0 for Knative Serving on OCP, K8s version v1.18.2.
2. Port-forward and listed metrics for the Controller pod, for a dump check here

It seems this is due to kubernetes/kubernetes#74636 check relevant discussion here kubernetes-sigs/controller-runtime#817. Not sure if this has been discussed before, I see a related comment here. Should we remove these metrics?

/cc @mattmoor @evankanderson @vaikas

[skonto]

I dug into the knative/pkg commit history, so the metrics have been stopped from being used from this commit Upgrade kubernetes-1.12.6 -> kubernetes-1.12.9 (#508) and on. Also have been removed from the upstream client-go repo here same date when they were stop being exposed from the k8s code. It is safe to remove or at least de-activate them by using some dummy provider as in here.