fix(helm): improve grafana dashboard (migrate newer grafana version and drop removed metrics)

Author: genofire

helm/dendrite/.helm-docs/monitoring.gotmpl

@@ -1,7 +1,7 @@
 {{ define "chart.monitoringSection" }}
 ## Monitoring
 
-[![Grafana Dashboard](https://grafana.com/api/dashboards/13916/images/9894/image)](https://grafana.com/grafana/dashboards/13916-dendrite/)
+![Grafana Dashboard](grafana_dashboards/dendrite-rev2.png)
 
 * Works well with [Prometheus Operator](https://prometheus-operator.dev/) ([Helmchart](https://artifacthub.io/packages/helm/prometheus-community/kube-prometheus-stack)) and their setup of [Grafana](https://grafana.com/grafana/), by enabling the following values:
 ```yaml

helm/dendrite/Chart.yaml

@@ -1,6 +1,6 @@
 apiVersion: v2
 name: dendrite
-version: "0.11.2"
+version: "0.11.3"
 appVersion: "0.11.1"
 description: Dendrite Matrix Homeserver
 type: application

helm/dendrite/README.md

@@ -1,7 +1,7 @@
 
 # dendrite
 
-![Version: 0.11.2](https://img.shields.io/badge/Version-0.11.2-informational?style=flat-square) ![Type: application](https://img.shields.io/badge/Type-application-informational?style=flat-square) ![AppVersion: 0.11.1](https://img.shields.io/badge/AppVersion-0.11.1-informational?style=flat-square)
+![Version: 0.11.3](https://img.shields.io/badge/Version-0.11.3-informational?style=flat-square) ![Type: application](https://img.shields.io/badge/Type-application-informational?style=flat-square) ![AppVersion: 0.11.1](https://img.shields.io/badge/AppVersion-0.11.1-informational?style=flat-square)
 Dendrite Matrix Homeserver
 
 Status: **NOT PRODUCTION READY**
@@ -158,7 +158,7 @@ Create a folder `appservices` and place your configurations in there.  The confi
 
 ## Monitoring
 
-[![Grafana Dashboard](https://grafana.com/api/dashboards/13916/images/9894/image)](https://grafana.com/grafana/dashboards/13916-dendrite/)
+![Grafana Dashboard](grafana_dashboards/dendrite-rev2.png)
 
 * Works well with [Prometheus Operator](https://prometheus-operator.dev/) ([Helmchart](https://artifacthub.io/packages/helm/prometheus-community/kube-prometheus-stack)) and their setup of [Grafana](https://grafana.com/grafana/), by enabling the following values:
 ```yaml