How to Hide the "Stripe Extensions" Admin Menu

function plt_hide_gf_stripe_extensions_menus() {
	//Hide the "Settings → Stripe Extensions" menu.
	remove_submenu_page('options-general.php', 'stripe-extensions');
}

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

Where do I put this code?