How to Hide the "Convert to Blocks" Admin Menu

function plt_hide_convert_to_blocks_menus() {
	//Hide the "Settings → Convert to Blocks" menu.
	remove_submenu_page('options-general.php', 'convert-to-blocks');
}

add_action('admin_menu', 'plt_hide_convert_to_blocks_menus', 11);

Where do I put this code?