Better IPA shader instruction implementation (#1082)

* Fix varying interpolation on fragment shader

* Some nits

* Alignment

Ryujinx.Graphics.Shader/ShaderProgram.cs

@@ -24,10 +24,5 @@ namespace Ryujinx.Graphics.Shader
         {
             Code = line + Environment.NewLine + Code;
         }
-
-        public void Replace(string name, string value)
-        {
-            Code = Code.Replace(name, value);
-        }
     }
 }