update minikube code example

Example 1: install minikube

curl -Lo minikube https://storage.googleapis.com/minikube/releases/latest/minikube-linux-amd64 \
  && chmod +x minikube

Example 2: brew minikube custom version install

curl -Lo minikube https://storage.googleapis.com/minikube/releases/latest/minikube-darwin-amd64 \
  && chmod +x minikube