remove unnecessary class name

com.unity.uiwidgets/Runtime/engine2/DisplayMetrics.cs

 #endif
 
 #if UNITY_IOS
-                _devicePixelRatioByDefault = DisplayMetrics.IOSDeviceScaleFactor();
+                _devicePixelRatioByDefault = IOSDeviceScaleFactor();
 #endif
 
                 if (_devicePixelRatioByDefault <= 0) {