Deprecate optional Knative Eventing components (#2788)

Signed-off-by: hansinikarunarathne <107214435+hansinikarunarathne@users.noreply.github.com>

example/kustomization.yaml

@@ -46,7 +46,8 @@ resources:
 - ../common/dex/overlays/oauth2-proxy
 # KNative
 - ../common/knative/knative-serving/overlays/gateways
-- ../common/knative/knative-eventing/base
+# Uncomment the following line if `knative-eventing` is required
+# - ../common/knative/knative-eventing/base
 - ../common/istio-1-22/cluster-local-gateway/base
 # Kubeflow namespace
 - ../common/kubeflow-namespace/base