New review comment by Chocimier on void-packages repository

https://github.com/void-linux/void-packages/pull/32856#discussion_r703021098

Comment:
In general it is less strict, I would (1) leave usage (no usage) as is except homepage, (2) use variable where it _means_ variable. That is: assume you can't use preferred pkgname. Would you use preferred, or actual pkgname there? If actual, use variable, otherwise spell out.