City range attack is increased by building walls and arsenals in your cities. If you want to change/remove those bonuses, look in buildingchanges.sql for CityRangedStrikeRange. You can modify the buildings there so they don't give the bonus.
If you modify walls, remember you will also need to modify babylon's walls. If you modify arsenal, remember you will also need to modify the Ostrog.
I couldn't really get this to work, it's still ranged attacks? Something else?