MINOR: trivial logCleanerEnable doc cleanup

Author: Manikumar Reddy O <manikumar.reddy@gmail.com>

Reviewers: Guozhang Wang <wangguoz@gmail.com>

Closes #1958 from omkreddy/MINOR-DOC-CHAGE

core/src/main/scala/kafka/server/KafkaConfig.scala

@@ -438,7 +438,7 @@ object KafkaConfig {
   "will allow more log to be cleaned at once but will lead to more hash collisions"
   val LogCleanerBackoffMsDoc = "The amount of time to sleep when there are no logs to clean"
   val LogCleanerMinCleanRatioDoc = "The minimum ratio of dirty log to total log for a log to eligible for cleaning"
-  val LogCleanerEnableDoc = "Enable the log cleaner process to run on the server? Should be enabled if using any topics with a cleanup.policy=compact including the internal offsets topic. If disabled those topics will not be compacted and continually grow in size."
+  val LogCleanerEnableDoc = "Enable the log cleaner process to run on the server. Should be enabled if using any topics with a cleanup.policy=compact including the internal offsets topic. If disabled those topics will not be compacted and continually grow in size."
   val LogCleanerDeleteRetentionMsDoc = "How long are delete records retained?"
   val LogCleanerMinCompactionLagMsDoc = "The minimum time a message will remain uncompacted in the log. Only applicable for logs that are being compacted."
   val LogIndexSizeMaxBytesDoc = "The maximum size in bytes of the offset index"