Minor script tweaks.

Assets/Scripts/TestConfigurationChooser.cs

 using System;
-using System.Text;
 using Unity.Collections;
 using UnityEngine.XR.ARSubsystems;
 using UnityEngine.XR.ARFoundation;
     public class TestConfigurationChooser : MonoBehaviour
     {
         /// <summary>
-        /// The AR session to set the configuration chooser.
+        /// The AR session on which to set the configuration chooser.
         /// </summary>
         public ARSession session
         {