improve uninstall documentation, remove None output in uninstall command

helpers/kubernetes.py

@@ -180,8 +180,10 @@ def delete_kustomization(kustomization_name):
     """
     Deletes a kustomization.
 
-    Note that this can also result in the deletion of an app's HelmReleases,
-    PVCs (user data!), OAuth2Client, etc. Nothing will remain
+    Note that if the kustomization has `prune: true` in its spec, this will
+    trigger deletion of other elements generated by the Kustomizartion. See
+    App.uninstall() to learn what implications this has for what will and will
+    not be deleted by the kustomize-controller.
 
     :param kustomization_name: name of the kustomization to delete
     :type kustomization_name: string