Remove unused command line short options -M and -N

The long options --multicast-addr and --multicast-port were
removed in commit c8c8869a.

tests/rigctld.c

@@ -81,7 +81,7 @@
  *      keep up to date SHORT_OPTIONS, usage()'s output and man page. thanks.
  * TODO: add an option to read from a file
  */
-#define SHORT_OPTIONS "m:r:p:d:P:D:s:S:c:T:t:C:W:w:x:z:lLuovhVZMRA:n:"
+#define SHORT_OPTIONS "m:r:p:d:P:D:s:S:c:T:t:C:W:w:x:z:lLuovhVZRA:"
 static struct option long_options[] =
 {
     {"model",           1, 0, 'm'},