Webhooks should be restricted to non openshift namespaces

[kannon92]

https://github.com/openshift/instaslice-operator/blob/main/config/default/namespace_selector_patch.yaml

Looking at this, I see that we don't want the webhooks for instaslice, cert-manager and "kube-system". I don't think "kube-system" is a legit namespace on an openshift cluster.

I think the list of namespaces would be a lot larger that we would want to exclude.