doc: remove multiple network resources with identical hostnames limitation

[KevFan]

Description

Closes: https://github.com/Kuadrant/kuadrant-operator/issues/702

https://github.com/Kuadrant/kuadrant-operator/issues/702 has been fixed and with the refactor to effective policies the limitatation for multiple network resources with identical hostnames no longer applies for Auth and RateLimit policy

Verification

• You can follow https://github.com/Kuadrant/kuadrant-operator/blob/main/doc/user-guides/auth-for-app-devs-and-platform-engineers.md but at step 4, create a HTTPRoute that defines the same hostname with a different path:

  kubectl apply -f - <<EOF
  apiVersion: gateway.networking.k8s.io/v1
  kind: HTTPRoute
  metadata:
  name: other
  spec:
  parentRefs:
  - name: kuadrant-ingressgateway
  namespace: gateway-system
  hostnames:
  - api.toystore.com
  rules:
  - matches: # rule-1
  - method: GET
    path:
      type: PathPrefix
      value: "/other"
  backendRefs:
  - name: toystore
    port: 80
  EOF

• Curling this path should give a 403 as it's protected by the GW policy

  curl -H 'Host: api.toystore.com'  http://$GATEWAY_URL/other -i