www/py-dj50-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 53c918e581b57e60dcc7139caae13e8dc945b773)