Silence static analysis warning

LGTM points out that since comparison with sizeof(buf) coerces n to
unsigned, all negative values become very large values, which are
necessarily larger than sizeof(buf), so the test is redundant. We still
want the test in our code to be explicit that we are checking for it, so
reordering the comparisons should silence the warning. A good optimizing
compiler should be able to combine the two conditions anyway.

See https://github.com/github/codeql/issues/4249

ncat/ncat_listen.c

@@ -1197,7 +1197,7 @@ static int chat_announce_disconnect(int fd)
 
     n = Snprintf(buf, sizeof(buf),
         "<announce> <user%d> is disconnected.\n", fd);
-    if (n >= sizeof(buf) || n < 0)
+    if (n < 0 || n >= sizeof(buf))
         return -1;
 
     return ncat_broadcast(&master_broadcastfds, &broadcast_fdlist, buf, n);