[SPARK-24531][TESTS] Replace 2.3.0 version with 2.3.1

## What changes were proposed in this pull request?

The PR updates the 2.3 version tested to the new release 2.3.1.

## How was this patch tested?

existing UTs

Author: Marco Gaido <marcogaido91@gmail.com>

Closes apache#21543 from mgaido91/patch-1.

Author: mgaido91

sql/hive/src/test/scala/org/apache/spark/sql/hive/HiveExternalCatalogVersionsSuite.scala

@@ -195,7 +195,7 @@ class HiveExternalCatalogVersionsSuite extends SparkSubmitTestUtils {
 
 object PROCESS_TABLES extends QueryTest with SQLTestUtils {
   // Tests the latest version of every release line.
-  val testingVersions = Seq("2.0.2", "2.1.2", "2.2.1", "2.3.0")
+  val testingVersions = Seq("2.0.2", "2.1.2", "2.2.1", "2.3.1")
 
   protected var spark: SparkSession = _