Update draft-ietf-quic-multipath.md

Co-authored-by: Kazuho Oku <[email protected]>

draft-ietf-quic-multipath.md

@@ -1019,7 +1019,7 @@ is an extension of the ACK frame defined by {{QUIC-TRANSPORT}}. It is
 used to acknowledge packets that were sent on different paths using
 multiple packet number spaces. If the frame type is TBD-01, ACK_MP frames
 also contain the sum of QUIC packets with associated ECN marks received
-on the acknowledged path up to this point.
+on the acknowledged packet number space up to this point.
 
 ACK_MP frame is formatted as shown in {{fig-ack-mp-format}}.