Add cleanup for GCPBackendPolicy

Author: nicolexin

site-src/guides/index.md

@@ -257,6 +257,7 @@ This quickstart guide is intended for engineers familiar with k8s and model serv
       ```bash
       kubectl delete -f https://github.com/kubernetes-sigs/gateway-api-inference-extension/raw/main/config/manifests/gateway/gke/gateway.yaml --ignore-not-found
       kubectl delete -f https://github.com/kubernetes-sigs/gateway-api-inference-extension/raw/main/config/manifests/gateway/gke/healthcheck.yaml --ignore-not-found
+      kubectl delete -f https://github.com/kubernetes-sigs/gateway-api-inference-extension/raw/main/config/manifests/gateway/gke/gcp-backend-policy.yaml --ignore-not-found
       kubectl delete -f https://github.com/kubernetes-sigs/gateway-api-inference-extension/raw/main/config/manifests/gateway/istio/gateway.yaml --ignore-not-found
       kubectl delete -f https://github.com/kubernetes-sigs/gateway-api-inference-extension/raw/main/config/manifests/gateway/istio/destination-rule.yaml --ignore-not-found
       kubectl delete -f https://github.com/kubernetes-sigs/gateway-api-inference-extension/raw/main/config/manifests/gateway/kgateway/gateway.yaml --ignore-not-found