Fix syntax error in menu example (#3499)

Author: Richienb

src/content/docs/learn/window-menu.mdx

@@ -280,7 +280,7 @@ fn main() {
         .setup(|app| {
             let menu_image = Image::from_bytes(include_bytes!("../icons/menu.png")).unwrap();
             let file_menu = SubmenuBuilder::new(app, "File")
-                .submenu_icon(menu_image)) // Optional: Add an icon to the submenu
+                .submenu_icon(menu_image) // Optional: Add an icon to the submenu
                 .text("open", "Open")
                 .text("quit", "Quit")
                 .build()?;