Comment 2 for bug 1858651

Assuming we do go through with removing heapster from CK 1.18, the kubernetes-master enable-dashboard-addons config description will need to be updated: https://github.com/charmed-kubernetes/charm-kubernetes-master/blob/daa8e11d70adb92e46853229ed88c57f4eeafc21/config.yaml#L65