Can’t delete the default jQuery in the theme

An example on how to deregister a WordPress built-in library and load your own:

function load_custom_scripts() {
    wp_deregister_script( 'jquery' );
    wp_register_script('jquery', '//code.jquery.com/jquery-2.2.4.min.js', array(), '2.2.4', true); // true will place script in the footer
    wp_enqueue_script( 'jquery' );
}
if(!is_admin()) {
    add_action('wp_enqueue_scripts', 'load_custom_scripts', 99);
}