Default shared cross hair for Serve Grafana dashboard

Author: anmol

python/ray/dashboard/modules/metrics/dashboards/serve_grafana_dashboard_base.json

@@ -14,7 +14,7 @@
   },
   "editable": true,
   "gnetId": null,
-  "graphTooltip": 0,
+  "graphTooltip": 1,
   "iteration": 1667344411089,
   "links": [],
   "panels": [],