MINOR: Add missing `+` in LogSegment.toString (#7408)

The closing `)` was previously being discarded.

Reviewers: Manikumar Reddy <manikumar.reddy@gmail.com>

core/src/main/scala/kafka/log/LogSegment.scala

@@ -412,7 +412,7 @@ class LogSegment private[log] (val log: FileRecords,
   override def toString: String = "LogSegment(baseOffset=" + baseOffset +
     ", size=" + size +
     ", lastModifiedTime=" + lastModified +
-    ", largestTime=" + largestTimestamp
+    ", largestTime=" + largestTimestamp +
     ")"
 
   /**