devel/glib20: Remove stale patch

This patch is guarding a deprecation warning for 11 years now.

Context: https://github.com/freebsd/freebsd-ports/commit/7887c684adab042fed1bfcba2e91589ecd17c4a8#r130575626

Tested by: arrowd
Sponsored by: Serenity Cybersecurity, LLC