x11/wayland-logout: unbreak build after 620968a43a5f

Partially revert until 12.3 + 3 months for 12.2 EOL (circa 2022Q2).
https://cgit.freebsd.org/src/commit/?id=925f44f33862
https://www.freebsd.org/releases/12.3R/schedule/

../wayland-logout.c:117:26: error: no member named 'cr_pid' in 'struct xucred'; did you mean 'cr_uid'?

ret = kill(peer_cred.pid, SIGTERM);
                     ^~~

../wayland-logout.c:120:65: error: no member named 'cr_pid' in 'struct xucred'; did you mean 'cr_uid'?

fprintf(stderr, "Error killing pid %d: %m\n", peer_cred.pid);
                                                        ^~~

Reported by: antoine
Pointy hat to: jbeich