To cleanup, follow the below steps.

To remove telemetry configuration / port-forward process

kubectl delete -f istio-telemetry.yaml

To remove the application virtual services / destination rules

kubectl delete -f samples/bookinfo/networking/virtual-service-all-v1.yaml

kubectl delete -f samples/bookinfo/networking/destination-rule-all.yaml

To remove the gateway / application

kubectl delete -f samples/bookinfo/networking/bookinfo-gateway.yaml

kubectl delete -f samples/bookinfo/platform/kube/bookinfo.yaml

To remove Istio

helm delete --purge istio
helm delete --purge istio-init