Fix implicit nullable to prevent deprecation on PHP 8.4

[vokomarov]

🔍 What was changed

Updated types delcaration to explicitly allow nullable where it is implicitly allowed.

🤔 Why?

To prevent deprecation errors while running it on PHP 8.4:

[ErrorException]
Cycle\Migrations\FileRepository::__construct(): Implicitly marking parameter $factory as nullable is deprecated, the explicit nullable type must be used instead
in vendor/cycle/migrations/src/FileRepository.php:42

📝 Checklist

• How was this tested:
  • Tested manually