remove toplevel argument.

src/Avalonia.Native/AvaloniaNativeMenuExporter.cs

@@ -133,7 +133,7 @@ namespace Avalonia.Native
 
             if (_nativeMenu is null)
             {
-                _nativeMenu = IAvnMenu.Create(_factory, false);
+                _nativeMenu = IAvnMenu.Create(_factory);
 
                 _nativeMenu.Initialise(this, appMenuHolder, "");
 
@@ -154,7 +154,7 @@ namespace Avalonia.Native
 
             if (_nativeMenu is null)
             {
-                _nativeMenu = IAvnMenu.Create(_factory, true);
+                _nativeMenu = IAvnMenu.Create(_factory);
 
                 _nativeMenu.Initialise(this, menu, "");     
 

src/Avalonia.Native/IAvnMenu.cs

@@ -39,11 +39,11 @@ namespace Avalonia.Native.Interop
 
         internal NativeMenu ManagedMenu { get; private set; }
 
-        public static IAvnMenu Create(IAvaloniaNativeFactory factory, bool isTopLevel)
+        public static IAvnMenu Create(IAvaloniaNativeFactory factory)
         {
             var events = new MenuEvents();
 
-            var menu = factory.CreateMenu(events, isTopLevel);
+            var menu = factory.CreateMenu(events);
 
             events.Initialise(menu);
 

src/Avalonia.Native/IAvnMenuItem.cs

@@ -114,7 +114,7 @@ namespace Avalonia.Native.Interop
             {
                 if (_subMenu == null)
                 {
-                    _subMenu = IAvnMenu.Create(factory, false);
+                    _subMenu = IAvnMenu.Create(factory);
 
                     _subMenu.Initialise(exporter, item.Menu, item.Header);