k8s: Disallow unknown fields in CNP & CCNP

Previously, the `x-kubernetes-preserve-unknown-fields` field was set to
true because it was incorrectly thought to have disallowed an empty spec
in a CNP / CCNP (empty rule). In reality, it is not needed at all, and
actually allows additional unknown fields to be permitted. Policies
such as the following would be allowed, bypassing the schema validation
of the CRD (note the `toFQDNs2`).

```
apiVersion: "cilium.io/v2"
kind: CiliumClusterwideNetworkPolicy
metadata:
  name: "denylist"
spec:
  endpointSelector:
    matchLabels:
      k8s-app.guestbook: web
  egress:
    - toEndpoints:
      - matchLabels:
          "k8s:io.kubernetes.pod.namespace": kube-system
          "k8s:k8s-app": kube-dns
      toPorts:
        - ports:
           - port: "53"
             protocol: ANY
          rules:
            dns:
              - matchPattern: "*"
    - toFQDNs2:
        - matchName: "www.google.com"
```

Fixes: 691f831 ("k8s, examples: Preserve unknown fields in {C,CC}NP")

Revert "k8s, examples: Preserve unknown fields in {C,CC}NP"
This reverts commit 691f831.

Reported-by: André Martins <andre@cilium.io>
Signed-off-by: Chris Tarazi <chris@isovalent.com>

pkg/k8s/apis/cilium.io/v2/ccnp_types.go

@@ -29,7 +29,6 @@ import (
 // +kubebuilder:resource:singular="ciliumclusterwidenetworkpolicy",path="ciliumclusterwidenetworkpolicies",scope="Cluster",shortName={ccnp}
 // +kubebuilder:subresource:status
 // +kubebuilder:storageversion
-// +kubebuilder:xpreserveunknownfields
 
 // CiliumClusterwideNetworkPolicy is a Kubernetes third-party resource with an
 // modified version of CiliumNetworkPolicy which is cluster scoped rather than

pkg/k8s/apis/cilium.io/v2/cnp_types.go

@@ -37,7 +37,6 @@ import (
 // +kubebuilder:printcolumn:JSONPath=".metadata.creationTimestamp",name="Age",type=date
 // +kubebuilder:subresource:status
 // +kubebuilder:storageversion
-// +kubebuilder:xpreserveunknownfields
 
 // CiliumNetworkPolicy is a Kubernetes third-party resource with an extended
 // version of NetworkPolicy.