Fix typo in Dd argument.

Author: 0-wiz-0

sbin/mount_union/mount_union.8

@@ -1,4 +1,4 @@
-.\"	$NetBSD: mount_union.8,v 1.18 2008/02/05 16:54:07 ad Exp $
+.\"	$NetBSD: mount_union.8,v 1.19 2009/05/04 20:11:30 wiz Exp $
 .\"
 .\" Copyright (c) 1994
 .\" The Regents of the University of California.  All rights reserved.
@@ -32,7 +32,7 @@
 .\"
 .\"	@(#)mount_union.8	8.7 (Berkeley) 5/1/95
 .\"
-.Dd Febuary 5, 2008
+.Dd February 5, 2008
 .Dt MOUNT_UNION 8
 .Os
 .Sh NAME