fix(doctrine): Doctrine 3 ApiPlatform\Doctrine\EventListener\PurgeHttpCacheListener uses deprecated ClassUtils class.

[wtfzdotnet]

Q	A
Branch?	3.2
Tickets	N/A
License	MIT
Doc PR	N/A

Waiting for unit tests to pass again on 3.2 so I can test further, just parking it here to make the issue known.

Remove deprecated ClassUtils from the PurgeHttpListener for doctrine 3, still need to check with due diligence and update tests, but these are failing right now.

[wtfzdotnet]

Can't for the life of me figure out why my local testsuite keeps failing at PHP Fatal error: Declaration of Doctrine\Bundle\MongoDBBundle\Form\DoctrineMongoDBTypeGuesser::guessType(string $class, string $property) must be compatible with Symfony\Component\Form\FormTypeGuesserInterface::guessType(string $class, string $property): ?Symfony\Component\Form\Guess\TypeGuess.

[soyuka]

thanks!