fix: update grafana dashboard docs (#11023)

Refer to the official Grafana dashboard

docs/metrics/prometheus/grafana/README.md

@@ -2,8 +2,6 @@
 
 [Grafana](https://grafana.com/) allows you to query, visualize, alert on and understand your metrics no matter where they are stored. Create, explore, and share dashboards with your team and foster a data driven culture.
 
-This document explains how to setup Grafana, to visualize MinIO metrics.
-
 ## Prerequisites
 
 - Prometheus and MinIO configured as explained in [document here](https://github.com/minio/minio/blob/master/docs/metrics/prometheus/README.md).
@@ -11,6 +9,6 @@ This document explains how to setup Grafana, to visualize MinIO metrics.
 
 ## MinIO Grafana Dashboard
 
-To start visualizing MinIO metrics exposed by MinIO, you can use our Grafana dashboard. Import to dashboard the contents from the [file here](https://github.com/minio/minio/blob/master/docs/metrics/prometheus/grafana/Minio-Overview-1594305200170.json).
+Visualize MinIO metrics, with our official Grafana dashboard available on the [Grafana dashboard portal](https://grafana.com/grafana/dashboards/13502).
 
 ![Grafana](https://raw.githubusercontent.com/minio/minio/master/docs/metrics/prometheus/grafana/grafana-minio.png)