I'm not 100% sure, but I believe if you don't include them in your weapon_orders file, it should just use the other weapons. Though, players will still get a knife every time they spawn. If you want to remove the knife from even then, let us know and we can write a simple script to do that.
The moment you remove knife, it may/cause animated issues with players looking like they have been crucified when they drop a weapon or are being given a new one. Just an advanced warning...there kisnt anything we can do about it.