Update beacon_nodes_Grafana_dashboard.json (#2744)

Changes `"datasource": null` to `"datasource: "Prometheus"` for all panels to avoid default in case Grafana has more datasources loaded and not using Prometheus as default.

grafana/beacon_nodes_Grafana_dashboard.json

@@ -152,7 +152,7 @@
       "bars": false,
       "dashLength": 10,
       "dashes": false,
-      "datasource": null,
+      "datasource": "Prometheus",
       "fieldConfig": {
         "defaults": {
           "custom": {},
@@ -250,7 +250,7 @@
       "bars": false,
       "dashLength": 10,
       "dashes": false,
-      "datasource": null,
+      "datasource": "Prometheus",
       "fieldConfig": {
         "defaults": {
           "custom": {},
@@ -360,7 +360,7 @@
       "bars": false,
       "dashLength": 10,
       "dashes": false,
-      "datasource": null,
+      "datasource": "Prometheus",
       "fieldConfig": {
         "defaults": {
           "custom": {},
@@ -463,7 +463,7 @@
       "bars": false,
       "dashLength": 10,
       "dashes": false,
-      "datasource": null,
+      "datasource": "Prometheus",
       "fieldConfig": {
         "defaults": {
           "custom": {},
@@ -564,7 +564,7 @@
       "bars": false,
       "dashLength": 10,
       "dashes": false,
-      "datasource": null,
+      "datasource": "Prometheus",
       "fieldConfig": {
         "defaults": {
           "custom": {},
@@ -671,7 +671,7 @@
       "bars": false,
       "dashLength": 10,
       "dashes": false,
-      "datasource": null,
+      "datasource": "Prometheus",
       "fieldConfig": {
         "defaults": {
           "custom": {},
@@ -768,7 +768,7 @@
       "bars": false,
       "dashLength": 10,
       "dashes": false,
-      "datasource": null,
+      "datasource": "Prometheus",
       "fieldConfig": {
         "defaults": {
           "custom": {},
@@ -879,7 +879,7 @@
         "rgba(237, 129, 40, 0.89)",
         "#d44a3a"
       ],
-      "datasource": null,
+      "datasource": "Prometheus",
       "description": "",
       "fieldConfig": {
         "defaults": {
@@ -969,7 +969,7 @@
         "rgba(237, 129, 40, 0.89)",
         "#d44a3a"
       ],
-      "datasource": null,
+      "datasource": "Prometheus",
       "description": "",
       "fieldConfig": {
         "defaults": {
@@ -1059,7 +1059,7 @@
         "rgba(237, 129, 40, 0.89)",
         "#d44a3a"
       ],
-      "datasource": null,
+      "datasource": "Prometheus",
       "description": "",
       "fieldConfig": {
         "defaults": {
@@ -1152,7 +1152,7 @@
         "rgba(237, 129, 40, 0.89)",
         "#d44a3a"
       ],
-      "datasource": null,
+      "datasource": "Prometheus",
       "fieldConfig": {
         "defaults": {
           "custom": {}
@@ -1243,7 +1243,7 @@
         "rgba(237, 129, 40, 0.89)",
         "#d44a3a"
       ],
-      "datasource": null,
+      "datasource": "Prometheus",
       "description": "",
       "fieldConfig": {
         "defaults": {
@@ -1338,7 +1338,7 @@
         "mode": "opacity"
       },
       "dataFormat": "tsbuckets",
-      "datasource": null,
+      "datasource": "Prometheus",
       "fieldConfig": {
         "defaults": {
           "custom": {}
@@ -1406,7 +1406,7 @@
         "rgba(237, 129, 40, 0.89)",
         "#d44a3a"
       ],
-      "datasource": null,
+      "datasource": "Prometheus",
       "description": "",
       "fieldConfig": {
         "defaults": {
@@ -1497,7 +1497,7 @@
         "rgba(237, 129, 40, 0.89)",
         "#d44a3a"
       ],
-      "datasource": null,
+      "datasource": "Prometheus",
       "description": "",
       "fieldConfig": {
         "defaults": {
@@ -1588,7 +1588,7 @@
         "rgba(237, 129, 40, 0.89)",
         "#d44a3a"
       ],
-      "datasource": null,
+      "datasource": "Prometheus",
       "decimals": null,
       "description": "",
       "fieldConfig": {
@@ -1681,7 +1681,7 @@
         "rgba(237, 129, 40, 0.89)",
         "#d44a3a"
       ],
-      "datasource": null,
+      "datasource": "Prometheus",
       "description": "",
       "fieldConfig": {
         "defaults": {
@@ -1772,7 +1772,7 @@
         "rgba(237, 129, 40, 0.89)",
         "#d44a3a"
       ],
-      "datasource": null,
+      "datasource": "Prometheus",
       "description": "",
       "fieldConfig": {
         "defaults": {
@@ -1869,7 +1869,7 @@
         "mode": "opacity"
       },
       "dataFormat": "tsbuckets",
-      "datasource": null,
+      "datasource": "Prometheus",
       "description": "",
       "fieldConfig": {
         "defaults": {
@@ -1944,7 +1944,7 @@
         "mode": "opacity"
       },
       "dataFormat": "tsbuckets",
-      "datasource": null,
+      "datasource": "Prometheus",
       "description": "",
       "fieldConfig": {
         "defaults": {
@@ -2019,7 +2019,7 @@
         "mode": "opacity"
       },
       "dataFormat": "tsbuckets",
-      "datasource": null,
+      "datasource": "Prometheus",
       "fieldConfig": {
         "defaults": {
           "custom": {}
@@ -2083,7 +2083,7 @@
       "bars": false,
       "dashLength": 10,
       "dashes": false,
-      "datasource": null,
+      "datasource": "Prometheus",
       "fieldConfig": {
         "defaults": {
           "custom": {},
@@ -2183,7 +2183,7 @@
       "bars": false,
       "dashLength": 10,
       "dashes": false,
-      "datasource": null,
+      "datasource": "Prometheus",
       "fieldConfig": {
         "defaults": {
           "custom": {},