[NavMenu] Do not use menu service for sub menu (#2771)

src/Core/Components/NavMenu/FluentNavGroup.razor

@@ -50,7 +50,8 @@
                     HorizontalPosition="@HorizontalPosition.End"
                     HorizontalInset="@false"
                     VerticalPosition="@VerticalPosition.Bottom"
-                    VerticalInset="@true">
+                    VerticalInset="@true"
+                    UseMenuService="false">
             @ChildContent
         </FluentMenu>
     }