Fix issue where a `ref` parameter would always be overwritten

src/Generator/Generators/CSharp/CSharpSources.cs

@@ -3313,7 +3313,7 @@ WriteLines($@"
             var argName = Generator.GeneratedIdentifier("arg") + paramIndex.ToString(CultureInfo.InvariantCulture);
             var paramMarshal = new ParamMarshal { Name = argName, Param = param };
 
-            if (param.IsOut || param.IsInOut)
+            if (param.IsOut)
             {
                 var paramType = param.Type;