www/py-django-post_office: Update 3.11 => 3.11.3

While here, sort Makefile (pet portclippy) and update pkg-descr.

Changelog:
https://github.com/ui/django-post_office/blob/v3.11.3/CHANGELOG.md

PR: 298057
Reported by: rottlog <rottlogg@proton.me> (author)
Approved by: osa, vvd (Mentors, implicit)
MFH: 2026Q3