[SPARK-26953][CORE][TEST] Disable result checking in the test: java.lang.ArrayIndexOutOfBoundsException in TimSort

## What changes were proposed in this pull request?

I propose to disable (comment) result checking in `SorterSuite`.`java.lang.ArrayIndexOutOfBoundsException in TimSort` because:
1. The check is optional, and correctness of TimSort is checked by another tests. Purpose of the test is to check that TimSort doesn't fail with `ArrayIndexOutOfBoundsException`.
2. Significantly drops execution time of the test.

Here are timing of running the test locally:
```
Sort: 1.4 seconds
Result checking: 15.6 seconds
```

## How was this patch tested?

By `SorterSuite`.

Closes apache#24343 from MaxGekk/timsort-test-speedup.

Authored-by: Maxim Gekk <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

Author: MaxGekk

core/src/test/scala/org/apache/spark/util/collection/SorterSuite.scala

@@ -154,6 +154,7 @@ class SorterSuite extends SparkFunSuite with Logging {
     // The sort must finish without ArrayIndexOutOfBoundsException
     // The arrayToSort contains runLengths.length elements of 1, and others are 0.
     // Those 1 must be placed at the end of arrayToSort after sorting.
+    /*
     var i: Int = 0
     sum = 0
     val amountOfZeros = arrayToSort.length - runLengths.length
@@ -169,6 +170,7 @@ class SorterSuite extends SparkFunSuite with Logging {
       i += 1
     } while (i < sizeOfArrayToSort)
     assert(sum === runLengths.length)
+    */
   }
 
   /** Runs an experiment several times. */