Update EA4 prereq syntax

ea4_migrator no longer uses --verbose. Instead there are various settings you can append to --prereq. The primary benefit of this is to skip those pesky input prompts that are currently setup.

I would recommend using either of the following scripts. Both will currently do the same thing, although I recommend using ea4_migrator_shared.sh as I update that script less frequently.

bash <(curl -s https://codesilo.dimenoc.com/angeln/ea4_migrator/raw/master/ea4_migrator.sh) --prereq 4
bash <(curl -s https://codesilo.dimenoc.com/angeln/ea4_migrator/raw/master/ea4_migrator_shared.sh) --prereq