Instructions to set up shared app gateway outdated

[amithkk]

Describe the bug The instruction to apply the CRD for AzureIngressProhibitedTarget is linked to an older revision on the repository with the apiVersion set to apiextensions.k8s.io/v1beta1. This no longer works with clusters that are above Kubernetes v1.22 since it has been deprecated. The following error appears:

error: resource mapping not found for name: "azureingressprohibitedtargets.appgw.ingress.k8s.io" namespace: "" from "https://raw.githubusercontent.com/Azure/application-gateway-kubernetes-ingress/ae695ef9bd05c8b708cedf6ff545595d0b7022dc/crds/AzureIngressProhibitedTarget.yaml": no matches for kind "CustomResourceDefinition" in version "apiextensions.k8s.io/v1beta1"

An updated version of the CRD exists in the repository, so it is simply a matter of updating the instructions to match.