[1.5.4] Fix issues.

Author: Yuncong Zhang

Runtime/material/bottom_navigation_bar.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Runtime.CompilerServices;
 using Unity.UIWidgets.animation;
 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.gestures;