[SPARK-23570][SQL] Add Spark 2.3.0 in HiveExternalCatalogVersionsSuite

## What changes were proposed in this pull request?
Add Spark 2.3.0 in HiveExternalCatalogVersionsSuite since Spark 2.3.0 is released for ensuring backward compatibility.

## How was this patch tested?
N/A

Author: gatorsmile <[email protected]>

Closes #20720 from gatorsmile/add2.3.

(cherry picked from commit 487377e)
Signed-off-by: gatorsmile <[email protected]>

Author: gatorsmile

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", "2.2.0", "2.2.1")
+  val testingVersions = Seq("2.0.2", "2.1.2", "2.2.0", "2.2.1", "2.3.0")
 
   protected var spark: SparkSession = _