www/py-django-cron: Deprecate/Set to expire

• Upstream project is inactive since 3+ years and there's no compatibility for Django 5.2 or newer.

• Although www/py-django42 will not reach its EoL until April, set the EXPIRATION_DATE accordingly at the end of 2026Q1 to get a clean cut with regard to the quarterly branch.

PR: 291707