Try this code:

add_filter( \'wp_targeted_link_rel\', \'__return_false\', 9999 );

function widget_text_replace($text) {
    $search = array(\'rel="noopener"\');
    $replace = array(\'\');
    $text = str_replace($search, $replace, $text);
    return $text;
}
add_filter(\'widget_text\', \'widget_text_replace\');