fix(gitlab-runner): Fix default datasource for dashboard

apps/base/gitlab-runner/dashboards/gitlab-runner-metrics.json

@@ -1459,6 +1459,23 @@
   "tags": ["gitlab-runner"],
   "templating": {
     "list": [
+      {
+        "current": {
+          "selected": false,
+          "text": "default",
+          "value": "default"
+        },
+        "hide": 0,
+        "includeAll": false,
+        "multi": false,
+        "name": "DS_PROMETHEUS",
+        "options": [],
+        "query": "prometheus",
+        "refresh": 1,
+        "regex": "default",
+        "skipUrlSync": false,
+        "type": "datasource"
+      },
       {
         "allValue": null,
         "current": {},