Remove ambiguity related to clusterType

Although it has been explicitly mentioned for
both GKE and EKS, it doesn't include other
environments like sandbox

doc/user/clusters/applications.md

@@ -417,6 +417,8 @@ You can check the recommended variables for each cluster type in the official do
 - [Google GKE](https://docs.cilium.io/en/stable/gettingstarted/k8s-install-gke/#deploy-cilium)
 - [AWS EKS](https://docs.cilium.io/en/stable/gettingstarted/k8s-install-eks/#deploy-cilium)
 
+Do not use `clusterType` for sandbox environments like [Minikube](https://minikube.sigs.k8s.io/docs/).
+
 You can customize Cilium's Helm variables by defining the
 `.gitlab/managed-apps/cilium/values.yaml` file in your cluster
 management project. Refer to the