devel/magit: Update to 3.3.0

• Switch to DISTVERSION
• Mark MAKE_JOBS_UNSAFE as parallel build fails if Emacs is built with native compilation enabled

ReleaseNotes: https://github.com/magit/magit/blob/master/Documentation/RelNotes/3.3.0.org
Approved by: meta (mentor)
Differential Revision: https://reviews.freebsd.org/D32309