Document BitTorrent tracker port usage

From https://github.com/erigontech/erigon/issues/15788 there are some extra ports a user was confused about. I came across https://docs.erigon.tech/fundamentals/default-ports?q=ports which might be used to compare against Docker compose port configurations and cause issues. AFAICT it's generated from https://github.com/erigontech/erigon/blob/main/README.md#default-ports-and-firewalls. We should mentioning the torrent tracker ports, and the procedure to disable them in there, which were described in https://github.com/erigontech/erigon/issues/15788#issuecomment-3515546276.