docs(apim): Only system-assigned managed identity is supported for SHGW & AD auth

Author: tomkerkhove

articles/api-management/self-hosted-gateway-enable-azure-ad.md

@@ -32,9 +32,13 @@ To enable Azure AD authentication, complete the following steps:
 
 * An API Management instance in the Developer or Premium service tier. If needed, complete the following quickstart: [Create an Azure API Management instance](get-started-create-service-instance.md).
 * Provision a [gateway resource](api-management-howto-provision-self-hosted-gateway.md) on the instance.
-* Enable a [managed identity](api-management-howto-use-managed-service-identity.md) on the instance.
+* Enable a [system-assigned managed identity](api-management-howto-use-managed-service-identity.md) on the instance.
 * Self-hosted gateway container image version 2.2 or later
 
+### Limitations notes
+
+* Only system-assigned managed identity is supported.
+
 ## Create custom roles
 
 Create the following two [custom roles](../role-based-access-control/custom-roles.md) that are assigned in later steps. You can use the permissions listed in the following JSON templates to create the custom roles using the [Azure portal](../role-based-access-control/custom-roles-portal.md), [Azure CLI](../role-based-access-control/custom-roles-cli.md), [Azure PowerShell](../role-based-access-control/custom-roles-powershell.md), or other Azure tools.
@@ -246,7 +250,6 @@ kubectl apply -f mygw.yaml
 
 [!INCLUDE [api-management-self-hosted-gateway-kubernetes-services](../../includes/api-management-self-hosted-gateway-kubernetes-services.md)]
 
-
 ## Next steps
 
 * Learn more about the API Management [self-hosted gateway overview](self-hosted-gateway-overview.md).