Remove Java version check from `IsolatedClientLoader`

val rootClassLoader: ClassLoader =
  if (SystemUtils.isJavaVersionAtLeast(JavaVersion.JAVA_9)) {
    // In Java 9, the boot classloader can see few JDK classes. The intended parent
    // classloader for delegation is now the platform classloader.
    // See http://java9.wtf/class-loading/
    val platformCL =
    classOf[ClassLoader].getMethod("getPlatformClassLoader").
      invoke(null).asInstanceOf[ClassLoader]
    // Check to make sure that the root classloader does not know about Hive.
    assert(Try(platformCL.loadClass("org.apache.hadoop.hive.conf.HiveConf")).isFailure)
    platformCL
  } else {
    // The boot classloader is represented by null (the instance itself isn't accessible)
    // and before Java 9 can see all JDK classes
    null
  }