add skip_magic_trailing_comma to black config
Created by: RoyStegeman
If a function input has a trailing comma black will not put the inputs on a single line, even if the line-length would be less than the specified length. I believe this is done to minimize diff, but I think it's undesirable: https://github.com/NNPDF/nnpdf/pull/1824#discussion_r1375994068