[doc] Tidy up Tor doc (more stringent)

This is a follow up to https://github.com/bitcoin/bitcoin/pull/19638 that left some deprectaed "hidden service/server" naming occurences.

It also shall make the chapter titles regarding creation of onion services stringent and easy to read and distinguish.

It removes the one and only reference to the testnet (here the testnet onion service port), as it is not explained that it references to the testnet and I do not know why it is mentioned there. It is only confusing. Also, as said, the testnet is not referenced at any other place in this document.

doc/tor.md

@@ -37,7 +37,7 @@ In a typical situation, this suffices to run behind a Tor proxy:
 	./bitcoind -proxy=127.0.0.1:9050
 
 
-## 2. Run a Bitcoin Core hidden server
+## 2. Manually create a Bitcoin Core onion service
 
 If you configure your Tor system accordingly, it is possible to make your node also
 reachable from the Tor network. Add these lines to your /etc/tor/torrc (or equivalent
@@ -46,7 +46,6 @@ versions of Tor see [Section 3](#3-automatically-listen-on-tor).*
 
 	HiddenServiceDir /var/lib/tor/bitcoin-service/
 	HiddenServicePort 8333 127.0.0.1:8334
-	HiddenServicePort 18333 127.0.0.1:18334
 
 The directory can be different of course, but virtual port numbers should be equal to
 your bitcoind's P2P listen port (8333 by default), and target addresses and ports
@@ -92,7 +91,7 @@ for normal IPv4/IPv6 communication, use:
 
 	./bitcoind -onion=127.0.0.1:9050 -externalip=57qr3yd1nyntf5k.onion -discover
 
-## 3. Automatically listen on Tor
+## 3. Automatically create a Bitcoin Core onion service
 
 Starting with Tor version 0.2.7.1 it is possible, through Tor's control socket
 API, to create and destroy 'ephemeral' onion services programmatically.
@@ -130,6 +129,6 @@ in the tor configuration file. The hashed password can be obtained with the comm
 
 - Do not add anything but Bitcoin Core ports to the onion service created in section 2.
   If you run a web service too, create a new onion service for that.
-  Otherwise it is trivial to link them, which may reduce privacy. Hidden
+  Otherwise it is trivial to link them, which may reduce privacy. Onion
   services created automatically (as in section 3) always have only one port
   open.