Make registration_expiration_helper service public
Make registration_expiration_helper service public

To fix: "User Deprecated: The
"surfnet_stepup.registration_expiration_helper" service is private,
getting it from the container is deprecated since Symfony 3.2 and will
fail in 4.0. You should either make the service public, or stop using
the container directly and use dependency injection instead."

SURFnet/Stepup-bundle,SURFnet/Stepup-bundle,SURFnet/Stepup-bundle