[SPARK-11500][SQL] Use sortBy instead of sortWith.

Author: HyukjinKwon

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetRelation.scala

@@ -398,7 +398,7 @@ private[sql] class ParquetRelation(
         val leaves = currentLeafStatuses.filter { f =>
           isSummaryFile(f.getPath) ||
             !(f.getPath.getName.startsWith("_") || f.getPath.getName.startsWith("."))
-        }.toArray.sortWith(_.getPath.toString < _.getPath.toString)
+        }.toArray.sortBy(_.getPath.toString)
 
         dataStatuses = leaves.filterNot(f => isSummaryFile(f.getPath))
         metadataStatuses =