Don't new a ScriptableObject

Author: keveleigh

Assets/MRTK/Tests/EditModeTests/Tools/MigrationToolTests.cs

@@ -79,7 +79,7 @@ public void ButtonMigrationTest()
             quadRenderer.sharedMaterial = testMat;
 
             ButtonConfigHelper buttonConfig = buttonGameObject.GetComponent<ButtonConfigHelper>();
-            ButtonIconSet testIconSet = new ButtonIconSet();
+            ButtonIconSet testIconSet = ScriptableObject.CreateInstance<ButtonIconSet>();
             buttonConfig.IconStyle = ButtonIconStyle.Quad;
             buttonConfig.IconSet = testIconSet;
             buttonConfig.EditorSetDefaultIconSet(testIconSet);