How to Hide the "Merge + Minify + Refresh" Admin Menu

function plt_hide_merge_minify_refresh_menus() {
	//Hide the "Settings → Merge + Minify + Refresh" menu.
	remove_submenu_page('options-general.php', 'merge-minify-refresh');
}

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

Where do I put this code?