Fix wrong format in JavaDocs #2

https://build.spring.io/browse/AMQP-MASTER-508

Author: artembilan

spring-amqp/src/main/java/org/springframework/amqp/core/AcknowledgeMode.java

@@ -39,7 +39,7 @@ public enum AcknowledgeMode {
 	 * Auto - the container will issue the ack/nack based on whether
 	 * the listener returns normally, or throws an exception.
 	 * <p><em>Do not confuse with RabbitMQ {@code autoAck} which is
-	 * represented by {@link #NONE} here<em>.
+	 * represented by {@link #NONE} here</em>.
 	 */
 	AUTO;