UploadedFileReferenceConverter: Use of hashService requires an additional secret

[ffrewer]

class WapplerSystems\FormExtended\Mvc\Property\TypeConverter\UploadedFileReferenceConverter, line 73:
$resourcePointer = $this->hashService->validateAndStripHmac($resourcePointerSource);

has to be changed:
https://docs.typo3.org/c/typo3/cms-core/main/en-us/Changelog/13.0/Deprecation-102763-ExtbaseHashService.html