Rephrase replication factor documentation (#3909)

* Fix docs on `RetryableTopic.replicationFactor()`

* Rephrase replicationFactor description about broker version

Signed-off-by: Seonghyeon Cho <seonghyeoncho96@gmail.com>

(cherry picked from commit ec154a3)

Author: sh-cho

spring-kafka/src/main/java/org/springframework/kafka/annotation/RetryableTopic.java

@@ -119,7 +119,7 @@
 	/**
 	 * The replication factor for the automatically created topics. Expressions must
 	 * resolve to a short or a String that can be parsed as such. Default is -1 to use the
-	 * broker default if the broker is earlier than version 2.4, an explicit value is
+	 * broker default. If the broker is earlier than version 2.4, an explicit value is
 	 * required.
 	 *
 	 * @return the replication factor.

spring-kafka/src/main/java/org/springframework/kafka/retrytopic/RetryTopicConfigurationBuilder.java

@@ -428,8 +428,8 @@ public RetryTopicConfigurationBuilder doNotAutoCreateRetryTopics() {
 	 * Configure the topic creation behavior to auto create topics with the provided
 	 * properties.
 	 * @param numPartitions the number of partitions.
-	 * @param replicationFactor the replication factor (-1 to use the broker default if the
-	 * broker is version 2.4 or later).
+	 * @param replicationFactor the replication factor (-1 to use the broker default. If the
+	 * broker is earlier than version 2.4, an explicit value is required).
 	 * @return the builder.
 	 */
 	public RetryTopicConfigurationBuilder autoCreateTopicsWith(@Nullable Integer numPartitions, @Nullable Short replicationFactor) {
@@ -443,8 +443,8 @@ public RetryTopicConfigurationBuilder autoCreateTopicsWith(@Nullable Integer num
 	 * properties.
 	 * @param shouldCreate true to auto create.
 	 * @param numPartitions the number of partitions.
-	 * @param replicationFactor the replication factor (-1 to use the broker default if the
-	 * broker is version 2.4 or later).
+	 * @param replicationFactor the replication factor (-1 to use the broker default. If the
+	 * broker is earlier than version 2.4, an explicit value is required).
 	 * @return the builder.
 	 */
 	public RetryTopicConfigurationBuilder autoCreateTopics(@Nullable Boolean shouldCreate, @Nullable Integer numPartitions,