Fix issues raised by phpstan

I think this might be a duplicate of 📌 deprecated class constant INITIAL_VALUES of class Drupal\address\Event\AddressEvents: Active .

Yes, they appear related. InitialValuesEvent is removed from address 2.0, so some change will be needed at least to the type declaration that uses it. I attempted to get it to pass for now with a test dependency, but that is not working.