Simplify code.

src/Compilers/Core/Portable/Serialization/IObjectWritable.cs

@@ -10,4 +10,4 @@ internal interface IObjectWritable
     {
         void WriteTo(ObjectWriter writer);
     }
-}
+}
\ No newline at end of file

src/Compilers/Core/Portable/Serialization/ObjectBinder.cs

@@ -2,8 +2,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Collections.Immutable;
-using System.Linq;
 
 namespace Roslyn.Utilities
 {