Deprecate --quic_ignore_invalid_error_code.

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 a9bf9c14b62bd5c9b651b66c7eb9e08e43146f74..6c3ad2b14449d9da0eb03e600ae692b7b2066d0e 100644
--- a/net/quic/quic_flags.cc
+++ b/net/quic/quic_flags.cc
@@ -95,10 +95,6 @@ bool FLAGS_quic_connection_defer_ack_response = true;
 // Resend 0RTT requests in response to an REJ that re-establishes encryption.
 bool FLAGS_quic_reply_to_rej = true;
 
-// If true, QuicFramer will ignore invalid error codes when processing GoAway,
-// ConnectionClose, and RstStream frames.
-bool FLAGS_quic_ignore_invalid_error_code = true;
-
 // If true, QUIC connections can do bandwidth resumption with an initial window
 // of < 10 packets.
 bool FLAGS_quic_no_lower_bw_resumption_limit = true;