devel/magit: Update to 3.3.0

[yasu]

Summary

• 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), ygy (mentor)

Test Plan

Build succeeds with poudriere and 13.0-RELEASE amd64 jail

[yasu]

Add 'Differential Revision:' to commit message.

[meta]

LGTM