add @deprecated tag to AwsIotMqttConnectionBuilder

Author: sbSteveK

sdk/src/main/java/software/amazon/awssdk/iot/AwsIotMqttConnectionBuilder.java

@@ -47,6 +47,7 @@
  * A central class for building Mqtt connections without manually managing a large variety of native objects (some
  * still need to be created though).
  */
+@Deprecated
 public final class AwsIotMqttConnectionBuilder extends CrtResource {
 
     private static String IOT_SIGNING_SERVICE = "iotdevicegateway";