docs: Add how to remove kube-proxy from existing clusters
docs: Add how to remove kube-proxy from existing clusters

Some users thought that it's not possible to remove kube-proxy from
existing installations. So, add instructions how to do that.

Also, remove the ask for specify a podCIDR (no longer needed).

Signed-off-by: Martynas Pumputis <6b0d31c0d563223024da45691584643ac78c96e8@lambda.lt>

michi-covalent/cilium,cilium/cilium,cilium/cilium,tklauser/cilium,tklauser/cilium,cilium/cilium,michi-covalent/cilium,tgraf/cilium,tklauser/cilium,tgraf/cilium,tgraf/cilium,tgraf/cilium,tgraf/cilium,tklauser/cilium,michi-covalent/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,cilium/cilium,tklauser/cilium,tgraf/cilium