Update link to custom authentication API

Author: gordonwang0

articles/iot-operations/manage-mqtt-connectivity/howto-configure-authentication.md

@@ -387,7 +387,7 @@ A sample custom authentication server and instructions are available on [GitHub]
 
 #### API
 
-The API between Azure IoT MQ and the custom authentication server follow the API specification for custom authentication. The OpenAPI specification is available on [GitHub](https://github.com/Azure-Samples/explore-iot-operations/blob/main/samples/auth-server-template/api.yaml).
+The API between Azure IoT MQ and the custom authentication server follow the API specification for custom authentication. The OpenAPI specification is available on [GitHub](https://github.com/Azure-Samples/explore-iot-operations/blob/main/samples/auth-server-template/api/0.5.0.yaml).
 
 #### HTTPS with TLS encryption is required