Deprecate --quic_include_path_id_in_iv.

net/quic/quic_flags.cc

Index: net/quic/quic_flags.cc
diff --git a/net/quic/quic_flags.cc b/net/quic/quic_flags.cc
index eea45d4ebcbcc1cc4ffef5a3c8e0267e3c87c818..9e4781d06c7574583d3ac0aaf69a57f63c979904 100644
--- a/net/quic/quic_flags.cc
+++ b/net/quic/quic_flags.cc
@@ -77,10 +77,6 @@ bool FLAGS_quic_supports_push_promise = false;
 // When turn on, log packet loss into transport connection stats LossEvent.
 bool FLAGS_quic_log_loss_event = true;
 
-// If true, for QUIC authenticated encryption algorithms, last 8 bytes
-// of IV comprise packet path id and lower 7 bytes of packet number.
-bool FLAGS_quic_include_path_id_in_iv = true;
-
 // If true, make sure new incoming streams correctly cede to higher
 // priority (or batch) streams when doing QUIC writes.
 bool FLAGS_quic_cede_correctly = true;