增加Pie和Radar的gridIndex支持设置指定网格

Runtime/Coord/Grid/GridLayoutContext.cs

@@ -6,10 +6,6 @@ namespace XCharts.Runtime
         public float y;
         public float width;
         public float height;
-        public float left;
-        public float right;
-        public float bottom;
-        public float top;
         public float eachWidth;
         public float eachHeight;
     }