function remove_my_action() {
    remove_action( 'wp_head', 'et_add_viewport_meta' );
}

function dt_et_add_viewport_meta() {
    echo '<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=5.0, user-scalable=1, viewport-fit=cover" />';
}

add_action( 'init', 'remove_my_action' );
add_action( 'wp_head', 'dt_et_add_viewport_meta' );