Support PHP 8.1

[rudenko-borys]

I have such deprecation on PHP 8.1
Deprecated: Return type of Knp\Bundle\GaufretteBundle\FilesystemMap::getIterator() should either be compatible with IteratorAggregate::getIterator(): Traversable, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /app/vendor/knplabs/knp-gaufrette-bundle/FilesystemMap.php on line 58

[eXsio]

+1, this msg heavily spams the logs.

[jukuan]

Here is my PR with correct fix:
https://github.com/KnpLabs/KnpGaufretteBundle/pull/259/files

[Nek-]

Here we are 🎉 ! Release 0.7.2 is compatible with PHP 8.1.