Update HOWTO.md
Update HOWTO.md

I just spent some time because I read the HOWTO instead of the readme to work with some project to find out that in only supports BSV. So I think updating this reference to the one from the readme makes sense
pooler/electrum-ltc-server,spesmilo/electrum-server,spesmilo/electrum-server,pooler/electrum-ltc-server