Fix compilation error iOS

Author: Sergio Alonso

Mixpanel/Controller.cs

@@ -10,6 +10,10 @@
 using Unity.Jobs;
 using Unity.Collections;
 
+#if UNITY_IOS
+using UnityEngine.iOS;
+#endif
+
 namespace mixpanel
 {
     internal class Controller : MonoBehaviour

Mixpanel/Worker.cs

@@ -10,10 +10,6 @@
 using System.Net.Http;
 using System.Web;
 
-#if UNITY_IOS
-using UnityEngine.iOS;
-#endif
-
 namespace mixpanel
 {
     public static partial class Worker