Fix producer for outputChannel

Current async version of the `KinesisMessageHandler` is request-reply.
The binder deals with it as a one-way, so no need in reply.

* Add `messageHandler.setOutputChannel(new NullChannel())` for the producer

spring-cloud-stream-binder-kinesis/src/main/java/org/springframework/cloud/stream/binder/kinesis/KinesisMessageChannelBinder.java

@@ -61,6 +61,7 @@
 import org.springframework.integration.aws.outbound.AbstractAwsMessageHandler;
 import org.springframework.integration.aws.outbound.KinesisMessageHandler;
 import org.springframework.integration.aws.outbound.KplMessageHandler;
+import org.springframework.integration.channel.NullChannel;
 import org.springframework.integration.core.MessageProducer;
 import org.springframework.integration.endpoint.MessageProducerSupport;
 import org.springframework.integration.expression.ExpressionUtils;
@@ -230,6 +231,7 @@ protected MessageHandler createProducerMessageHandler(ProducerDestination destin
 		messageHandler.setAsync(!producerProperties.getExtension().isSync());
 		messageHandler.setSendTimeout(producerProperties.getExtension().getSendTimeout());
 		messageHandler.setBeanFactory(getBeanFactory());
+		messageHandler.setOutputChannel(new NullChannel());
 
 		if (errorChannel != null) {
 			((InterceptableChannel) channel)