Update draft-ietf-quic-recovery.md

Co-Authored-By: Martin Thomson <mt@lowentropy.net>

draft-ietf-quic-recovery.md

@@ -576,7 +576,7 @@ dictated by packet and time threshold mechanisms; see {{ack-loss-detection}}.
 A Retry packet causes a client to send another Initial packet, effectively
 restarting the connection process.  A Retry packet indicates that the Initial
 was received, but not processed.  A Retry packet cannot be treated as an
-acknowledgment, because it does not indicate a packet was processed or
+acknowledgment, because it does not indicate that a packet was processed or
 specify the packet number.
 
 Clients that receive a Retry packet reset congestion control and loss recovery