Fixing a test race condition

The test testDlqWithNativeSerializationEnabledOnDlqProducer fails on CI occasionally.
Adding a sleep of 1 second to give the retrying mechanism enough time to complete.

spring-cloud-stream-binder-kafka/src/test/java/org/springframework/cloud/stream/binder/kafka/KafkaBinderTests.java

@@ -544,6 +544,8 @@ public class KafkaBinderTests extends
 		Message<?> receivedMessage = receive(dlqChannel, 5);
 		assertThat(receivedMessage).isNotNull();
 		assertThat(receivedMessage.getPayload()).isEqualTo("foo".getBytes());
+		//Adding a 1 second sleep to give the retrying enough time to complete. 
+		Thread.sleep(1000);
 		assertThat(handler.getInvocationCount())
 				.isEqualTo(consumerProperties.getMaxAttempts());
 		assertThat(receivedMessage.getHeaders()