release: Remove remnants of pc98 support

The cons25w line was added in c991a64747 for pc98, along with reading
MACHINE in order to determine what terminal type to use for VTYs. Commit
2b375b4edd removed this condition, leaving it as always using xterm
for VTYs, but left behind the now-unused MACHINE variable and the
cons25w list entry. Clean these up to be how they were before pc98
support was added.

Note that anyone who really needs a cons25w terminal can still request
it, it's just not listed as a common option.

Reviewed by:	imp, brooks
Differential Revision:	https://reviews.freebsd.org/D36587

release/rc.local

@@ -8,8 +8,6 @@
 : ${BSDDIALOG_ESC=5}
 : ${BSDDIALOG_ERROR=255}
 
-MACHINE=`uname -m`
-
 # resolv.conf from DHCP ends up in here, so make sure the directory exists
 mkdir /tmp/bsdinstall_etc
 
@@ -40,7 +38,6 @@ else
 	echo "   ansi     Standard ANSI terminal"
 	echo "   vt100    VT100 or compatible terminal"
 	echo "   xterm    xterm terminal emulator (or compatible)"
-	echo "   cons25w  cons25w terminal"
 	echo
 	echo -n "Console type [vt100]: "
 	read TERM