Added a note about multi-resource support

Multi-resource metric alert rules aren't supported for Virtual Machines at this point.

Author: harelbr

articles/azure-government/documentation-government-services-monitoringandmanagement.md

@@ -174,6 +174,9 @@ The resources currently supported in the second generation alerts experience are
 - Microsoft.Web/sites
 - Microsoft.Web/sites/slots
 
+> [!NOTE]
+> Creating multi-resource metric alert rules on Virtual Machines is **currently not supported**. This article will be updated as soon as this functionality becomes available.
+
 You can still use [classic alerts](../azure-monitor/platform/alerts-classic.overview.md) for resources not yet available in the second generation of alerts. 
 
 When using PowerShell/ARM/Rest calls to create metric alerts, you will need to set the "Location" of the metric alert to "USGov Virginia" or "USGov Iowa". An example of the setting is below:
@@ -186,6 +189,7 @@ Add-AzMetricAlertRule -Name vmcpu_gt_1 -Location "USGov Virginia" -ResourceGroup
 
 For more information on using PowerShell, see [public documentation](../azure-monitor/platform/powershell-quickstart-samples.md).
 
+
 ## Application Insights
 
 > [!NOTE]