docs(alerting): admonition for webhook features that are not GA in GC (#104331)

* docs(alerting): admonition for webhook features that are not GA in GC

* fix plural

* minor copy change

docs/sources/alerting/configure-notifications/manage-contact-points/integrations/webhook-notifier.md

@@ -254,6 +254,12 @@ The Alert object represents an alert included in the notification group, as prov
 
 ## Custom Payload
 
+{{< admonition type="note" >}}
+
+Custom Payload is not yet [generally available](https://grafana.com/docs/release-life-cycle/#general-availability) in Grafana Cloud.
+
+{{< /admonition >}}
+
 The `Custom Payload` option allows you to completely customize the webhook payload using templates. This gives you full control over the structure and content of the webhook request.
 
 | Option            | Description                                                                                               |

docs/sources/alerting/configure-notifications/template-notifications/reference.md

@@ -269,6 +269,12 @@ You can then use `tz` to change the timezone from UTC to local time, such as `Eu
 
 ## Namespaced Functions
 
+{{< admonition type="note" >}}
+
+Namespaced Functions are not yet [generally available](https://grafana.com/docs/release-life-cycle/#general-availability) in Grafana Cloud.
+
+{{< /admonition >}}
+
 In addition to the top-level functions, the following namespaced functions are also available:
 
 ### Collection Functions