doc: remove multiple network resources with identical hostnames limitation

[KevFan]

Description

Closes: #702

#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