ports/duemilanove: Remove quotes around ISP devices

This avoids confusing *roff as it removes a quote from the
begining of the line.

Signed-off-by: Keith Packard <keithp@keithp.com>

ports/duemilanove/snek-duemilanove-install.1

@@ -23,8 +23,8 @@ Duemilanove board.
 .SH OPTIONS
 .TP
 \-isp <ISP model>
-Specifies the programmer to use, common options are 'optiboot', 
-'usbtiny', and 'avrisp2'. The default is 'optiboot'.
+Specifies the programmer to use, common options are optiboot, 
+usbtiny, and avrisp2. The default is optiboot.
 .TP
 \-hex <snek.hex>
 Specifies the hex file to load to the board. The default is the