Monitoring: Fix max CPU usage graph

nixos/modules/monitoring/server/grafana-dashboards/resources-overview.json

@@ -116,7 +116,7 @@
       "pluginVersion": "8.3.5",
       "targets": [
         {
-          "expr": "1 - (max by (instance) (irate(node_cpu_seconds_total{mode=\"idle\"}[5m])))",
+          "expr": "1 - (min by (instance) (irate(node_cpu_seconds_total{mode=\"idle\"}[5m])))",
           "interval": "",
           "intervalFactor": 1,
           "legendFormat": "{{instance}}",