[LIVY-1025][TEST] Clean up Python2InterpreterSpec post Python deprecation

## What changes were proposed in this pull request?

 * Cleans up Python2InterpreterSpec since python 2 is deprecated.
 * Also removed the Python2SessionSpec counterpart

## How was this patch tested?

 * CI

Author: ArnavBalyan

repl/src/test/scala/org/apache/livy/repl/PythonInterpreterSpec.scala

@@ -278,32 +278,7 @@ abstract class PythonBaseInterpreterSpec extends BaseInterpreterSpec {
   }
 }
 
-class Python2InterpreterSpec extends PythonBaseInterpreterSpec {
-
-  implicit val formats = DefaultFormats
-
-  override def createInterpreter(): Interpreter = {
-    val sparkConf = new SparkConf()
-    PythonInterpreter(sparkConf, new SparkEntries(sparkConf))
-  }
-
-  // Scalastyle is treating unicode escape as non ascii characters. Turn off the check.
-  // scalastyle:off non.ascii.character.disallowed
-  it should "print unicode correctly" in withInterpreter { intp =>
-    intp.execute("print(u\"\u263A\")") should equal(Interpreter.ExecuteSuccess(
-      TEXT_PLAIN -> "\u263A"
-    ))
-    intp.execute("""print(u"\u263A")""") should equal(Interpreter.ExecuteSuccess(
-      TEXT_PLAIN -> "\u263A"
-    ))
-    intp.execute("""print("\xE2\x98\xBA")""") should equal(Interpreter.ExecuteSuccess(
-      TEXT_PLAIN -> "\u263A"
-    ))
-  }
-  // scalastyle:on non.ascii.character.disallowed
-}
-
-class Python3InterpreterSpec extends PythonBaseInterpreterSpec with BeforeAndAfterAll {
+class PythonInterpreterSpec extends PythonBaseInterpreterSpec with BeforeAndAfterAll {
 
   implicit val formats = DefaultFormats
 

repl/src/test/scala/org/apache/livy/repl/PythonSessionSpec.scala

@@ -170,8 +170,6 @@ abstract class PythonSessionSpec extends BaseSessionSpec(PySpark) {
   }
 }
 
-class Python2SessionSpec extends PythonSessionSpec
-
 class Python3SessionSpec extends PythonSessionSpec with BeforeAndAfterAll {
 
   override protected def withFixture(test: NoArgTest): Outcome = {