Deprecate -ingester.ring.readiness-check-ring-health

[pracucci]

I propose to deprecate -ingester.ring.readiness-check-ring-health. It defaults to false and we're not using it in jsonnet or Helm. Nowadays that ingesters requires persistency and so are deployed in K8S as StatefulSet, I don't see any need to enable it, and I suggest to deprecate the option (and the remove it after 2 releases).