Deprecation notices on PHP 8.4 (implicitly nullable parameters)

[sebastianmulders]

Using PHP 8.4 and the latest version of fastly/fastly-php (v12), I'm seeing several deprecation notices related to implicitly nullable parameters.

For example:

PHP Deprecated: Fastly\Api\PurgeApi::__construct(): Implicitly marking parameter $client as nullable is deprecated, the explicit nullable type must be used instead in /vendor/fastly/fastly/lib/Api/PurgeApi.php on line 72
PHP Deprecated: Fastly\Model\PurgeResponse::__construct(): Implicitly marking parameter $data as nullable is deprecated, the explicit nullable type must be used instead in /vendor/fastly/fastly/lib/Model/PurgeResponse.php on line 178

There might be more instances with PHP 8.4.

A patch for these would be greatly appreciated. Happy to contribute with a PR if helpful.