Update Grafana RP registration in AMW subscrption for ARM template

Author: bragi92

articles/azure-monitor/essentials/prometheus-metrics-enable.md

@@ -114,6 +114,7 @@ The output will be similar to the following:
 ### Prerequisites
 
 - Register the `AKS-PrometheusAddonPreview` feature flag in the Azure Kubernetes clusters subscription with the following command in Azure CLI: `az feature register --namespace Microsoft.ContainerService --name AKS-PrometheusAddonPreview`.
+- If the Azure Managed Grafana instance is in a subscription other than the Azure Monitor Workspaces subscription then please register the Azure Monitor Workspace subscrption with the `Microsoft.Dashboard` resource provider following this [documenation](https://learn.microsoft.com/en-us/azure/azure-resource-manager/management/resource-providers-and-types#register-resource-provider)
 - The Azure Monitor workspace and Azure Managed Grafana workspace must already be created.
 - The template needs to be deployed in the same resource group as the Azure Managed Grafana workspace.