Use only equals in UnsafeRow sort before repartition

sql/core/src/main/scala/org/apache/spark/sql/execution/exchange/ShuffleExchangeExec.scala

@@ -358,7 +358,7 @@ object ShuffleExchangeExec {
             UnsafeExternalRowSorter.PrefixComputer.Prefix = {
               // The hashcode generated from the binary form of a [[UnsafeRow]] should not be null.
               result.isNull = false
-              result.value = row.hashCode()
+              result.value = 42
               result
             }
           }