Slight change to tier benefits (Dreamer) (Patreon)

Hey, guys. I made as slight change to the commission benefit for Dreamer-tier patrons. I've limited the discount to premium tier commissions only.

This change will take effect on the next round of commissions; anyone that has a current commission with me for another tier will still get the 20% off the price.

I'm going to tru to think of some ways to actually add to this tier going forward (rather than subtract).