Add hint to section "Blocking Https Advertisement Assets" that it is only needed for Pihole version < 4.0

[kyondev]

WARNING: I'm not 100% sure about this. So please excuse me if this issue was a mistake/is wrong.

As far as I have understood it, as of version 4.0 of Pi-hole there is no need to execute the iptables commands listet in the "Blocking Https Advertisement Assets" section here.
Reason as to why I think this is an issue: The edit "Update: 2018-08-06" in the top post

[dschaper]

The default blocking method did change with version 4 to no longer use the Pi-hole IP address. However you can still use that method if you require the blocking page so the iptables directions do still apply. There's no risk of breakage if you do have those rules in your chains so I think everything is okay?

[kyondev]

This is just a cosmetic issue. Did not want people unnecessarily having to run the commands when they do not provide any benefits for the new default blocking mode.
So this means the hint should be that this is only useful when using BLOCKINGMODE=IP.