textproc/multimarkdown: update 6.5.2 to 6.6.0
- Update to 6.6.0;
- Update cheat sheet to latest snapshot.
Release Notes: https://github.com/fletcher/MultiMarkdown-6/releases/tag/6.5.3 https://github.com/fletcher/MultiMarkdown-6/releases/tag/6.6.0
PR: 250703
Submitted by: Yasuhiro KIMURA <yasu % utahime.org>