Invalid type hints in Action class

[patk95]

Action::$error has wrong type (only |null) hints:

• hetzner-cloud-php-sdk/src/Models/Actions/Action.php

  Line 46 in 8cff31f

  * @var |null

• hetzner-cloud-php-sdk/src/Models/Actions/Action.php

  Line 60 in 8cff31f

  * @param null| $error

This causes issues with tools like e.g. PHPStan.