Remove stale reference to wtmp(5).

Reported by:	pluknet

sbin/reboot/reboot.8

@@ -28,7 +28,7 @@
 .\"	@(#)reboot.8	8.1 (Berkeley) 6/9/93
 .\" $FreeBSD$
 .\"
-.Dd June 9, 1993
+.Dd October 11, 2010
 .Dt REBOOT 8
 .Os
 .Sh NAME
@@ -129,7 +129,7 @@ utility is used when the system needs to be halted or restarted, giving
 users advance warning of their impending doom and cleanly terminating
 specific programs.
 .Sh SEE ALSO
-.Xr wtmp 5 ,
+.Xr getutxent 3 ,
 .Xr boot 8 ,
 .Xr dumpon 8 ,
 .Xr nextboot 8 ,