www/py-dj51-django-taggit: Sync with 8ac1760ada10
- Remove defunct testsuite because upstream no longer supplies it in the sdist tarballs since release 6.0.0.
- Switch to PEP517 build framework while I'm here.
- Bump PORTREVISION due changed package contents.
MFH: 2025Q2
(cherry picked from commit ee26544d25d875ee3038076ced2e9a6d121c72a9)