Clarify that SHA3 digests are truncted in RELAY_SENDME messages
We do indeed document that the body of a version-1 sendme is 20 bytes long. But we don't (AFAIK) document that we truncate other hashes to this length: let's do that.
We do indeed document that the body of a version-1 sendme is 20 bytes long. But we don't (AFAIK) document that we truncate other hashes to this length: let's do that.