Remove rkt references from Installing Kubernetes with Minikube page

[aimeeu]

This is a Bug Report

Problem:
rkt is no longer a valid container option (the project is being archived). However, rkt is mentioned in two sections.

Proposed Solution:
Remove references to rkt as a container runtime. It is no longer supported by minikube.
https://minikube.sigs.k8s.io/docs/reference/runtimes/

Page to Update:
k8s.io/docs/setup/learning-environment/minikube/
https://kubernetes.io/docs/setup/learning-environment/minikube/#minikube-features
https://kubernetes.io/docs/setup/learning-environment/minikube/#starting-a-cluster-on-alternative-container-runtimes

[aimeeu]

/assign

[sftim]

Final cleanup done in #24531