Remove flex shorthand getter because it doesnt make a lot of sense

Summary: It doesn't make sense to have a getter for the shorthand as it is the computed flexGrow and flexShrink values that you should care about.

Reviewed By: gkassabli

Differential Revision: D4064674

fbshipit-source-id: 69935b85042020b4e8c61a393c1be8f4d42a6674

csharp/Facebook.CSSLayout/CSSNode.cs

@@ -310,12 +310,6 @@ namespace Facebook.CSSLayout
 
         public float Flex
         {
-            get
-            {
-                AssertNativeInstance();
-                return Native.CSSNodeStyleGetFlex(_cssNode);
-            }
-
             set
             {
                 AssertNativeInstance();

csharp/Facebook.CSSLayout/Native.cs

@@ -164,9 +164,6 @@ namespace Facebook.CSSLayout
         [DllImport(DllName)]
         public static extern void CSSNodeStyleSetFlex(IntPtr node, float flex);
 
-        [DllImport(DllName)]
-        public static extern float CSSNodeStyleGetFlex(IntPtr node);
-
         [DllImport(DllName)]
         public static extern void CSSNodeStyleSetFlexGrow(IntPtr node, float flexGrow);