Documented all $id parameters in API classes as int

[morozov]

When analyzing code which uses GitHub API, static analyzers like PHPStan may produce false positives like:

↪ phpstan analyse -l 7 src tests
 3/3 [▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓] 100%

 ------ -------------------------------------------------------------------------------------- 
  Line   src/Changeset.php                                                                     
 ------ -------------------------------------------------------------------------------------- 
  120    Parameter #3 $id of method Github\Api\PullRequest::show() expects string, int given.  
 ------ -------------------------------------------------------------------------------------- 

According to the documentation, all changed $ids are integers.

[acrobat]

Thanks @morozov!