Fix the section reference

In recovery for max_ack_delay of 0.

Came from #3459

draft-ietf-quic-recovery.md

@@ -465,7 +465,7 @@ network roundtrip-time (smoothed_rtt), the variation in the estimate (4*rttvar),
 and max_ack_delay, to account for the maximum time by which a receiver might
 delay sending an acknowledgement.  When the PTO is armed for Initial or
 Handshake packet number spaces, the max_ack_delay is 0, as specified in
-13.2.5 of {{QUIC-TRANSPORT}}.
+13.2.1 of {{QUIC-TRANSPORT}}.
 
 The PTO value MUST be set to at least kGranularity, to avoid the timer expiring
 immediately.