Fix issue with TransportException

[sam-bee]

To enable to the TransportException code to be accessed in PHP < 8.1 make reflection property accessible

Without this change, I get this error in PHP versions below 8.1:

$ composer why-not [package name] [version]

In Application.php line 449:
                                                                                 
  Cannot access non-public member Composer\Downloader\TransportException::$code  
                                                                                 

prohibits [-r|--recursive] [-t|--tree] [--locked] [--] <package> <version>

This issue seems to have been introduced in Composer 2.7.5.

This bug will not be present with PHP 8.1 +, according to setAccessible docs.

[Seldaek]

Oh oops yes sorry about that.

[Seldaek]

And thanks for the fix :)