Document the -a option in .Fl form instead of .Cm form to be consistant

with the rest of the manpage.  (Lite2 documents it in getopt form, Lite1
did it in old-style arg format)

sbin/dump/dump.8

@@ -31,7 +31,7 @@
 .\" SUCH DAMAGE.
 .\"
 .\"     @(#)dump.8	8.3 (Berkeley) 5/1/95
-.\"	$Id: dump.8,v 1.12 1997/02/22 14:32:16 peter Exp $
+.\"	$Id: dump.8,v 1.13 1997/03/11 12:09:31 peter Exp $
 .\"
 .Dd May 1, 1995
 .Dt DUMP 8
@@ -73,7 +73,7 @@ multiple volumes.
 On most media the size is determined by writing until an
 end-of-media indication is returned.  This can be enforced
 by using the
-.Cm a
+.Fl a
 option.
 .Pp
 On media that cannot reliably return an end-of-media indication