Fix parameter name binding in Change Signature Dialog

src/VisualStudio/Core/Def/Implementation/ChangeSignature/ChangeSignatureDialog.xaml

@@ -203,7 +203,7 @@
                             </Style>
                         </DataGridTextColumn.ElementStyle>
                     </DataGridTextColumn>
-                    <DataGridTextColumn x:Name="parameterHeader" Binding="{Binding Parameter, Mode=OneWay}" IsReadOnly="True">
+                    <DataGridTextColumn x:Name="parameterHeader" Binding="{Binding ParameterName, Mode=OneWay}" IsReadOnly="True">
                         <DataGridTextColumn.ElementStyle>
                             <Style TargetType="TextBlock">
                                 <Setter Property="Padding" Value="{StaticResource ResourceKey=cellPadding}" />