www/py-django42: Deprecate/Set to expire
- Set a deprecation note and let it expire to the end of May to give enough time to switch all affected ports over to Django 5.2 which is the next LTS release.
The plan is to make every consumer ready for Django 5.2 during 2026Q1 and then switch everything to Django 5.2 after 2026Q2 has branched.
PR: 291707
With hat: python
Differential Revision: https://reviews.freebsd.org/D54248