Update api-management-howto-manage-protocols-ciphers.md

Fixes https://github.com/MicrosoftDocs/azure-docs/issues/102957

Author: dlepow

articles/api-management/api-management-howto-manage-protocols-ciphers.md

@@ -25,6 +25,7 @@ By default, API Management enables TLS 1.2 for client and backend connectivity a
 
 > [!NOTE]
 > * If you're using the self-hosted gateway, see [self-hosted gateway security](self-hosted-gateway-overview.md#security) to manage TLS protocols and cipher suites.
+> * Currently, API Management doesn't support TLS 1.3.
 > * The Consumption tier doesn't support changes to the default cipher configuration. 
 
 ## Prerequisites