Weed brownie iuse

Create an iuse function so that the weed brownies implemented in #7615 actually have the weed effect. I'd also like to suggest possibly reducing the charges down from 8, since that seems like a little much to get out of one brownie, unless it's a whole pan. Would you be alright with reducing charges @Hibou48888?

Edit: ~~Wasn't sure what "bool b" is for, and included it because I noticed it in the weed iuse. However I noticed that quite a few of the other functions simply have "bool" without actually assigning a variable, and I noticed an unused parameter warning when compiling (since I'm, obviously, not using the variable). Should I remove the b? What does it represent?~~ Answered on IRC, thanks Kevin

In addition, should I change the use message or is there a way to suppress the "You eat the special brownie" message? It looks a little silly when you have both messages occur.