Add instructions to remove docker images; fixes #6874 (#7264)

* Add instructions to remove docker images; fixes #6874

On cleanup of Minikube, adds instructions to optionally remove Docker images created in tutorial setup

* update wording of instructions to include flag

Updates the wording to explicitly match the shell command and flags used.

docs/tutorials/stateless-application/hello-minikube.md

@@ -393,6 +393,12 @@ kubectl delete service hello-node
 kubectl delete deployment hello-node
 ```
 
+Optionally, force removal of the Docker images created:
+
+```shell
+docker rmi hello-node:v1 hello-node:v2 -f
+```
+
 Optionally, stop the Minikube VM:
 
 ```shell