Add in option for btcpay_backup to backup full lnd state for migration

[johnheenan]

The deleted line removes the failure to backup lnd database files channel.db and sphinxreplay.db.

Please see https://github.com/lightningnetwork/lnd/discussions/9070 for issue and discussion.

I suspect the next line should also be deleted for CLN:

    --exclude="volumes/generated_clightning_bitcoin_datadir/_data/lightning-rpc" \