if (!function_exists('remove_wp_open_sans')) {
    function remove_wp_open_sans() {
        wp_deregister_style('open-sans');
        wp_register_style('open-sans', false);
    }
}
// 前台删除Google字体CSS
add_filter('wp_enqueue_scripts', 'remove_wp_open_sans');
// 后台删除Google字体CSS
add_filter('admin_enqueue_scripts', 'remove_wp_open_sans');