Added return void annotation to suppress deprecation warnings in Command::configure()

[mickverm]

When version 3.4.3 of this bundle is used together with Symfony 6.3 (Symfony 6.3.0-BETA1), the following warning is logged:

Method "Symfony\Component\Console\Command\Command::configure()" might add "void" as a native return type declaration in the future. Do the same in child class "Doctrine\Bundle\FixturesBundle\Command\LoadDataFixturesDoctrineCommand" now to avoid errors or add an explicit @return annotation to suppress this message.