Bump golangci-lint to v1.20.0
Bump golangci-lint to v1.20.0

This version comes with significant memory improvements, making some
adjustments for small memory footprint in the CI obsolete.

dlorenc/minikube,dlorenc/minikube,kubernetes/minikube,warmchang/minikube,kubernetes/minikube,warmchang/minikube,dlorenc/minikube,kubernetes/minikube,dlorenc/minikube,dlorenc/minikube,kubernetes/minikube,warmchang/minikube,warmchang/minikube,dlorenc/minikube,dalehamel/minikube,warmchang/minikube,dlorenc/minikube,warmchang/minikube,dalehamel/minikube,kubernetes/minikube,dalehamel/minikube,kubernetes/minikube,dlorenc/minikube,warmchang/minikube,kubernetes/minikube