Update custom-domains-certificates.md

Update doc to mention that you cannot add a custom domain that contains the environment DNS suffix to your Container App.

Author: gabesmsft

articles/container-apps/custom-domains-certificates.md

@@ -19,7 +19,7 @@ Azure Container Apps allows you to bind one or more custom domains to a containe
 - Ingress must be enabled for the container app
 
 > [!NOTE]
-> To configure a custom DNS suffix for all container apps in an environment, see [Custom environment DNS suffix in Azure Container Apps](environment-custom-dns-suffix.md).
+> To configure a custom DNS suffix for all container apps in an environment, see [Custom environment DNS suffix in Azure Container Apps](environment-custom-dns-suffix.md). If you configure a custom environment DNS suffix, you cannot add a custom domain that contains this suffix to your Container App.
 
 ## Add a custom domain and certificate