[SPARK-18132] Fix checkstyle

This PR fixes checkstyle.

Author: Yin Huai <yhuai@databricks.com>

Closes #15656 from yhuai/fix-format.

core/src/main/java/org/apache/spark/util/collection/unsafe/sort/UnsafeExternalSorter.java

@@ -143,9 +143,10 @@ public final class UnsafeExternalSorter extends MemoryConsumer {
     this.recordComparator = recordComparator;
     this.prefixComparator = prefixComparator;
     // Use getSizeAsKb (not bytes) to maintain backwards compatibility for units
-    // this.fileBufferSizeBytes = (int) conf.getSizeAsKb("spark.shuffle.file.buffer", "32k") * 1024;
+    // this.fileBufferSizeBytes = (int) conf.getSizeAsKb("spark.shuffle.file.buffer", "32k") * 1024
     this.fileBufferSizeBytes = 32 * 1024;
-    // The spill metrics are stored in a new ShuffleWriteMetrics, and then discarded (this fixes SPARK-16827).
+    // The spill metrics are stored in a new ShuffleWriteMetrics,
+    // and then discarded (this fixes SPARK-16827).
     // TODO: Instead, separate spill metrics should be stored and reported (tracked in SPARK-3577).
     this.writeMetrics = new ShuffleWriteMetrics();