Refactor simplify partitionSubset logic

Signed-off-by: Su Ko <rhtn1128@gmail.com>

Author: bandalgomsu

spring-kafka/src/main/java/org/springframework/kafka/listener/ConcurrentMessageListenerContainer.java

@@ -60,6 +60,7 @@
  * @author Tomaz Fernandes
  * @author Wang Zhiyang
  * @author Lokesh Alamuri
+ * @author Su Ko
  */
 public class ConcurrentMessageListenerContainer<K, V> extends AbstractMessageListenerContainer<K, V> {