x11-wm/picom: Update 12.5 => 13

While here, remove deprecated DRM option.

Changelog:
https://github.com/yshui/picom/releases/tag/v13

PR: 295255
Reported by: José Maldonado <yukiteruamano@volfread.xyz> (maintainer)
Approved by: osa, vvd (Mentors, implicit)
MFH: 2026Q2

(cherry picked from commit 515d560673177472fb9d4c9e3c8c7e763fc5d6a8)