Require x11-base/xorg-server 21.1.14 on Gentoo

[radarhere]

gentoo is currently failing in main - https://github.com/python-pillow/docker-images/actions/runs/11641137059/job/32419281238

#16 4.755 !!! Multiple package instances within a single package slot have been pulled
#16 4.755 !!! into the dependency graph, resulting in a slot conflict:
#16 4.755
#16 4.755 x11-base/xorg-server:0
#16 4.755
#16 4.755 (x11-base/xorg-server-21.1.14:0/21.1.14::gentoo, ebuild scheduled for merge) USE="elogind udev xorg xvfb -debug -minimal (-selinux) -suid -systemd -test -unwind -xcsecurity -xephyr -xnest" ABI_X86="(64)" pulled in by
#16 4.755 x11-base/xorg-server[xvfb] required by (x11-misc/xvfb-run-21.1.7.1:0/0::gentoo, ebuild scheduled for merge) USE="" ABI_X86="(64)"
#16 4.755 ^^^^
#16 4.755
#16 4.755 (x11-base/xorg-server-21.1.13-r1-2:0/21.1.13::gentoo, binary scheduled for merge) USE="elogind udev xorg -debug -minimal (-selinux) -suid -systemd -test -unwind -xcsecurity -xephyr -xnest -xvfb" ABI_X86="(64)" pulled in by
#16 4.755 x11-base/xorg-server:0/21.1.13= required by (x11-drivers/xf86-video-dummy-0.4.1-6:0/0::gentoo, binary scheduled for merge) USE="" ABI_X86="(64)"
#16 4.755 ^^^^^^^^^^^
#16 4.755 (and 2 more with the same problem)
#16 4.755
#16 4.755 NOTE: Use the '--verbose-conflicts' option to display parents omitted above
#16 4.755
#16 4.756
#16 4.756 The following USE changes are necessary to proceed:
#16 4.756 (see "package.use" in the portage(5) man page for more details)
#16 4.756 # required by x11-misc/xvfb-run-21.1.7.1::gentoo
#16 4.756 # required by x11-misc/xvfb-run (argument)
#16 4.756 >=x11-base/xorg-server-21.1.14 xvfb

Adding =x11-base/xorg-server-21.1.14 fixes the failure.