Remove prep time.

[CaptOle]

Even though long prep times may be very tedious and somewhat unneeded on Beginner, Normal, and the early waves of Hard, it is pretty much essential for success in Rag and Hard in later waves. Time to build up a base, repair shields, refill ammo, etc. is very much needed since the time between the bots reaching the shieldwall may be too short for anything to be done effectively.