The TLS draft says in https://quicwg.github.io/base-drafts/draft-ietf-quic-tls.html#rfc.section.9.1.2:

Endpoints MUST NOT use an ACK frame in an unprotected packet to acknowledge packets that were protected by 0-RTT or 1-RTT keys. An endpoint MUST treat receipt of an ACK frame in an unprotected packet that claims to acknowledge protected packets as a connection error of type OPTIMISTIC_ACK.

The Loss Recovery draft currently says that unprotected packets containing ACKs for protected packets have to be ignored. This PR updates the Loss Recovery draft and makes it consistent with the TLS draft.