Made test randomizer serializable to better reflect the test use case

com.unity.perception/Tests/Editor/RandomizerEditorTests.cs

+using System;
+using Object = UnityEngine.Object;
 
 namespace EditorTests
 {
         }
     }
 
+    [Serializable]
     [AddRandomizerMenu("Test Randomizers/Errors OnCreate Test Randomizer")]
     class ErrorsOnCreateTestRandomizer : Randomizer
     {
         {
             // This line should throw a NullReferenceException
             testGameObject.transform.position = Vector3.zero;
-        }
-
-        protected override void OnIterationStart()
-        {
-            testGameObject = new GameObject("Test");
         }
     }
 }