[MINOR][CORE][TEST] Remove unnecessary sort in UnsafeInMemorySorterSuite

## What changes were proposed in this pull request?

We don't require specific ordering of the input data, the sort action is not necessary and misleading.

## How was this patch tested?

Existing test suite.

Author: Xingbo Jiang <[email protected]>

Closes #21536 from jiangxb1987/sorterSuite.

Author: jiangxb1987

core/src/test/java/org/apache/spark/util/collection/unsafe/sort/UnsafeInMemorySorterSuite.java

@@ -129,7 +129,6 @@ public int compare(
     final UnsafeSorterIterator iter = sorter.getSortedIterator();
     int iterLength = 0;
     long prevPrefix = -1;
-    Arrays.sort(dataToSort);
     while (iter.hasNext()) {
       iter.loadNext();
       final String str =