Disable "assigned but never used" warning on non-iOS

Assets/Scenes/ARKitCoachingOverlay/ARKitCoachingOverlay.cs

 
     [SerializeField]
     [Tooltip("The coaching goal associated with the coaching overlay.")]
+#if !UNITY_IOS
+    #pragma warning disable CS0414
+#endif
+#if !UNITY_IOS
+    #pragma warning restore CS0414
+#endif
 
 #if UNITY_IOS
     /// <summary>