less sketchy drawings, "done right"

This rectifies an issue with commit 5028b4acd6dbac72b924bcf7c7004db36c4201fa:

changing the sketchiness value in mp-sketch doesn't do one any good as it'll be then changed in `Illustrations/config.mp`, which is the place for inter-illustration config options.

The diff reverts the change made to `mp-sketch`, and applies it to `config` {1}.

{1} However, config already had it set to 2.25pt (~2.24bp), thus I lowered it to 1.8pt (~1.79bp) instead.