Change Kafka cleanup.on-shutdown default to false

Align our property with the recently changed spring-kafka default.

Closes gh-25730

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/kafka/KafkaProperties.java

@@ -1264,7 +1264,7 @@ public class KafkaProperties {
 		/**
 		 * Cleanup the application’s local state directory on shutdown.
 		 */
-		private boolean onShutdown = true;
+		private boolean onShutdown = false;
 
 		public boolean isOnStartup() {
 			return this.onStartup;