remove unnecessary IOSDeviceStartup call

Runtime/Plugins/platform/ios/UIWidgetsViewController.mm

 
 extern "C"
 {
-    void IOSDeviceStartup()
-    {
-        [[UIWidgetsViewController sharedInstance] tryLaunch];
-    }
-
     viewMetrics IOSGetViewportPadding()
     {
         viewMetrics metrics;

Runtime/engine/DisplayMetrics.cs

                     padding_bottom = 0
                 };
 #elif UNITY_IOS
-                IOSDeviceStartup();
                 viewMetrics metrics = IOSGetViewportPadding();
                 this._viewMetrics = metrics;
 #else
 
 		[DllImport("__Internal")]
 		static extern viewMetrics IOSGetViewportPadding();
-
-        [DllImport("__Internal")]
-        static extern void IOSDeviceStartup();
 #endif
 
     }