How to Hide Proxy Cache Purge Admin Menus

function plt_hide_varnish_http_purge_menus() {
	//Hide "Proxy Cache".
	remove_menu_page('varnish-page');
	//Hide "Proxy Cache → Settings".
	remove_submenu_page('varnish-page', 'varnish-page');
	//Hide "Proxy Cache → Check Caching".
	remove_submenu_page('varnish-page', 'varnish-check-caching');
	//Hide "Proxy Cache → Get Cache Warming".
	remove_submenu_page('varnish-page', 'vhp-cache-warming');
}

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

Where do I put this code?