x11-servers/xorg-server: Update to 21.1.13

Release notes: https://lists.x.org/archives/xorg-announce/2024-April/003504.html

Differential Revision: https://reviews.freebsd.org/D44794
Reviewed by: bapt
PR: 278381
Sponsored by: Beckhoff Automation GmbH & Co. KG

(cherry picked from commit a6d4f50ada9d185e74d40a9f0698534b5bf7ad1d)