getBounces() $messageID argument has wrong type #163

Hey, I'm currently updating some legacy code and upgrading various packages, came across an issue that I was able to trace back to what I'm fairly certain is a typo bug in this package.

Our code is pulling any bounces based on a given specific Postmark message ID (e.g. an ID like 454ef8fc-da5f-4662-b6d6-74a54d78504d):

$bounces = $postmark_client->getBounces(1, 0, NULL, NULL, NULL, NULL, $message_id);

But it was failing because: Postmark\PostmarkClient::getBounces(): Argument #7 ($messageID) must be of type ?int, string given

Looks like this $messageID argument was changed from string to int in commit c7a4371 ("Update to level 5 PHPStan"), and based on context clues, I think it was just a simple oversight/typo, understandable when updating so much code at once (I've been there).

Changing int to string in my local copy of PostmarkClient.php fixed this issue for me.