Remove "Stage" variable

as we will use distinct Influx and Grafana instances for the different stages/environments.

deploy/grafana-dashboard/queries/runner-per-minute.flux

@@ -6,7 +6,6 @@ result = from(bucket: "poseidon")
   |> range(start: date.truncate(t: v.timeRangeStart, unit: 1m), stop: date.truncate(t: v.timeRangeStop, unit: 1m))
   |> filter(fn: (r) => r["_measurement"] == "poseidon_used_runners")
   |> filter(fn: (r) => contains(value: r["environment_id"], set: ${environment_ids:json}))
-  |> filter(fn: (r) => (not exists r.stage) or contains(value: r["stage"], set: ${stages:json}))
   |> filter(fn: (r) => r["event_type"] == "creation")
   |> group(columns: ["environment_id", "stage"], mode:"by")
   |> aggregateWindow(every: 1m, fn: count, createEmpty: true)