doc: remove mentions of UPnP

doc/tor.md

@@ -200,7 +200,7 @@ as well, use `discover` instead:
 
     ./bitcoind ... -discover
 
-and open port 8333 on your firewall (or use port mapping, i.e., `-upnp` or `-natpmp`).
+and open port 8333 on your firewall (or use port mapping, i.e., `-natpmp`).
 
 If you only want to use Tor to reach .onion addresses, but not use it as a proxy
 for normal IPv4/IPv6 communication, use: