Remove reference to get-k8s-versions

Since PR kubernetes/minikube#2911, get-k8s-versions option has been
removed. Reference this option in documentation is not needed any more.

content/en/docs/setup/minikube.md

@@ -218,6 +218,7 @@ To switch back to this context later, run this command: `kubectl config use-cont
 
 #### Specifying the Kubernetes version
 
+Minikube supports running multiple different versions of Kubernetes. 
 You can specify the specific version of Kubernetes for Minikube to use by
 adding the `--kubernetes-version` string to the `minikube start` command. For
 example, to run version `v1.7.3`, you would run the following: