Make MenuItem check mark visible with Simple theme (#15424)

* Make MenuItem check mark visible with Simple theme

Signed-off-by: AnErrupTion <[email protected]>

* Fix for radio menu items

Signed-off-by: AnErrupTion <[email protected]>

* Remove useless setter

Signed-off-by: AnErrupTion <[email protected]>

---------

Signed-off-by: AnErrupTion <[email protected]>

src/Avalonia.Themes.Simple/Controls/MenuItem.xaml

@@ -105,7 +105,7 @@
       <Setter Property="Opacity" Value="{DynamicResource ThemeDisabledOpacity}" />
     </Style>
     
-    <Style Selector="^:toggle /template/ Viewbox#PART_ToggleIconPresenter, ^:radio /template/ Viewbox#PART_ToggleIconPresenter">
+    <Style Selector="^:toggle /template/ ContentControl#PART_ToggleIconPresenter, ^:radio /template/ ContentControl#PART_ToggleIconPresenter">
       <Setter Property="IsVisible" Value="True" />
     </Style>
     <Style Selector="^:toggle /template/ ContentPresenter#PART_IconPresenter, ^:radio /template/ ContentPresenter#PART_IconPresenter">