[Documentation:] azurerm_monitor_scheduled_query_rules_alert - Add wa…

…rning and reference to _v2 resource (#26553)

website/docs/r/monitor_scheduled_query_rules_alert.html.markdown

@@ -10,6 +10,8 @@ description: |-
 
 Manages an AlertingAction Scheduled Query Rules resource within Azure Monitor.
 
+-> **Warning** This resource is using an older AzureRM API version which is known to cause problems e.g. with custom webhook properties not included in triggered alerts. This resource is superseded by the [azurerm_monitor_scheduled_query_rules_alert_v2](./monitor_scheduled_query_rules_alert_v2.html.markdown) resource using newer API versions.
+
 ## Example Usage
 
 ```hcl