How to Hide the "PDFjs Viewer" Admin Menu

function plt_hide_pdfjs_viewer_shortcode_menus() {
	//Hide the "Settings → PDFjs Viewer" menu.
	remove_submenu_page('options-general.php', 'pdfjs');
}

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

Where do I put this code?