[SPARK-45344][CORE][SQL] Remove all Scala version string check

### What changes were proposed in this pull request?
This PR removes all the no longer needed Scala version string checks.

### Why are the changes needed?
These version checks are no longer needed.

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?
Pass GitHub Actions

### Was this patch authored or co-authored using generative AI tooling?
No

Closes #43133 from LuciferYang/SPARK-45344.

Authored-by: yangjie01 <[email protected]>
Signed-off-by: yangjie01 <[email protected]>

Author: LuciferYang

core/src/main/scala/org/apache/spark/serializer/KryoSerializer.scala

@@ -26,7 +26,6 @@ import javax.annotation.Nullable
 import scala.collection.mutable.ArrayBuffer
 import scala.jdk.CollectionConverters._
 import scala.reflect.ClassTag
-import scala.util.Properties
 import scala.util.control.NonFatal
 
 import com.esotericsoftware.kryo.{Kryo, KryoException, Serializer => KryoClassSerializer}
@@ -229,9 +228,7 @@ class KryoSerializer(conf: SparkConf)
 
     kryo.register(None.getClass)
     kryo.register(Nil.getClass)
-    if (Properties.versionNumberString.startsWith("2.13")) {
-      kryo.register(Utils.classForName("scala.collection.immutable.ArraySeq$ofRef"))
-    }
+    kryo.register(Utils.classForName("scala.collection.immutable.ArraySeq$ofRef"))
     kryo.register(Utils.classForName("scala.collection.immutable.$colon$colon"))
     kryo.register(Utils.classForName("scala.collection.immutable.Map$EmptyMap$"))
     kryo.register(Utils.classForName("scala.math.Ordering$Reverse"))

core/src/test/scala/org/apache/spark/deploy/rest/SubmitRestProtocolSuite.scala

@@ -19,8 +19,6 @@ package org.apache.spark.deploy.rest
 
 import java.lang.Boolean
 
-import scala.util.Properties.versionNumberString
-
 import org.json4s.jackson.JsonMethods._
 
 import org.apache.spark.{SparkConf, SparkFunSuite}
@@ -235,34 +233,7 @@ class SubmitRestProtocolSuite extends SparkFunSuite {
       |}
     """.stripMargin
 
-  private lazy val submitDriverRequestJson = if (versionNumberString.startsWith("2.12")) {
-    s"""
-      |{
-      |  "action" : "CreateSubmissionRequest",
-      |  "appArgs" : [ "two slices", "a hint of cinnamon" ],
-      |  "appResource" : "honey-walnut-cherry.jar",
-      |  "clientSparkVersion" : "1.2.3",
-      |  "environmentVariables" : {
-      |    "PATH" : "/dev/null"
-      |  },
-      |  "mainClass" : "org.apache.spark.examples.SparkPie",
-      |  "sparkProperties" : {
-      |    "spark.archives" : "fireballs.zip",
-      |    "spark.driver.extraLibraryPath" : "pickle.jar",
-      |    "spark.jars" : "mayonnaise.jar,ketchup.jar",
-      |    "spark.driver.supervise" : "false",
-      |    "spark.app.name" : "SparkPie",
-      |    "spark.cores.max" : "10000",
-      |    "spark.driver.memory" : "${Utils.DEFAULT_DRIVER_MEM_MB}m",
-      |    "spark.files" : "fireball.png",
-      |    "spark.driver.cores" : "180",
-      |    "spark.driver.extraJavaOptions" : " -Dslices=5 -Dcolor=mostly_red",
-      |    "spark.executor.memory" : "256m",
-      |    "spark.driver.extraClassPath" : "food-coloring.jar"
-      |  }
-      |}
-    """.stripMargin
-  } else {
+  private lazy val submitDriverRequestJson =
     s"""
       |{
       |  "action" : "CreateSubmissionRequest",
@@ -289,7 +260,6 @@ class SubmitRestProtocolSuite extends SparkFunSuite {
       |  }
       |}
     """.stripMargin
-  }
 
   private val submitDriverResponseJson =
     """

core/src/test/scala/org/apache/spark/serializer/KryoSerializerSuite.scala

@@ -553,7 +553,6 @@ class KryoSerializerSuite extends SparkFunSuite with SharedSparkContext {
   }
 
   test("SPARK-43898: Register scala.collection.immutable.ArraySeq$ofRef for Scala 2.13") {
-    assume(scala.util.Properties.versionNumberString.startsWith("2.13"))
     val conf = new SparkConf(false)
     conf.set(KRYO_REGISTRATION_REQUIRED, true)
     val ser = new KryoSerializer(conf).newInstance()

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

@@ -162,9 +162,8 @@ class HiveSparkSubmitSuite
     // Before the fix in SPARK-8470, this results in a MissingRequirementError because
     // the HiveContext code mistakenly overrides the class loader that contains user classes.
     // For more detail, see sql/hive/src/test/resources/regression-test-SPARK-8489/*scala.
-    // TODO: revisit for Scala 2.13 support
     val version = Properties.versionNumberString match {
-      case v if v.startsWith("2.12") || v.startsWith("2.13") => v.substring(0, 4)
+      case v if v.startsWith("2.13") => v.substring(0, 4)
       case x => throw new Exception(s"Unsupported Scala Version: $x")
     }
     val jarDir = getTestResourcePath("regression-test-SPARK-8489")