1.7.0.2 で再導入されたようですhttps://github.com/PrestaShop/PrestaShop/pull/7022代わりにregisterJavascriptとregisterStylesheet
を使用します。
$this->registerJavascript('remote-bootstrap-head', 'https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js', ['server' => 'remote', 'position' => 'head', 'priority' => 20]);
$this->registerJavascript('remote-bootstrap', 'https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js', ['server' => 'remote', 'position' => 'bottom', 'priority' => 20]);
$this->registerStylesheet('remote-bootstrap', 'https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css', ['server' => 'remote', 'priority' => 20]);