Fix OnCall Insights dashboard version (#3917)

# What this PR does

## Which issue(s) this PR fixes

## Checklist

- [ ] Unit, integration, and e2e (if applicable) tests updated
- [x] Documentation added (or `pr:no public docs` PR label added if not
required)
- [x] `CHANGELOG.md` updated (or `pr:no changelog` PR label added if not
required)

grafana-plugin/src/dashboards/oncall_metrics_dashboard.json

@@ -1490,6 +1490,6 @@
   },
   "timezone": "browser",
   "title": "OnCall Insights",
-  "version": 3,
+  "version": 2,
   "weekStart": ""
 }