add_action(
    'mastodon_api_unreact',
    function (
        $post_id,
        $this-_get_reaction_for_status_action,
        string $favourite
    ) {
        // Your code here
    },
    10,
    3
);

do_action( 'mastodon_api_unreact', $post_id, $this->get_reaction_for_status_action( 'favourite' ), 'favourite' )

do_action( 'mastodon_api_unreact', $post_id, $this->get_reaction_for_status_action( 'bookmark' ), 'bookmark' )