QUIC: removed check for in-flight packets in computing PTO. The check is needed for clients in order to unblock a server due to anti-amplification limits, and it seems to make no sense for servers. See RFC 9002, A.6 and A.8 for a further explanation. This makes max_ack_delay to now always account, notably including PATH_CHALLENGE timers as noted in the last paragraph of 9000, 9.4, unlike when it was only used when there are packets in flight. While here, fixed nearby style.