deprecate -FLAGS_quic_reloadable_flag_quic_disable_version_34 and remove support for QUIC v34.

net/quic/core/quic_flags_list.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file intentionally does not have header guards, it's included
 // inside a macro to generate values.
 
 // This file contains the list of QUIC protocol flags.
 
 // If true, QUIC BBR congestion control may be enabled via Finch and/or via QUIC
@@ skipping 107 matching lines @@
 QUIC_FLAG(bool,
           FLAGS_quic_reloadable_flag_quic_fix_cubic_bytes_quantization,
           false)
 
 // If true, fix Cubic\'s use of kBetaLastMax for n-connection emulation.
 QUIC_FLAG(bool, FLAGS_quic_reloadable_flag_quic_fix_beta_last_max, false)
 
 // If true, enable QUIC v37.
 QUIC_FLAG(bool, FLAGS_quic_reloadable_flag_quic_enable_version_37, true)
 
-// If true, disables QUIC v34.
-QUIC_FLAG(bool, FLAGS_quic_reloadable_flag_quic_disable_version_34, true)
-
 // If greater than zero, mean RTT variation is multiplied by the specified
 // factor and added to the congestion window limit.
 QUIC_FLAG(double, FLAGS_quic_bbr_rtt_variation_weight, 0.0f)
 
 // Congestion window gain for QUIC BBR during PROBE_BW phase.
 QUIC_FLAG(double, FLAGS_quic_bbr_cwnd_gain, 2.0f)
 
 // If true, bidi streaming is always enabled in QUIC.
 QUIC_FLAG(bool,
           FLAGS_quic_reloadable_flag_quic_always_enable_bidi_streaming,
@@ skipping 65 matching lines @@
 QUIC_FLAG(bool, FLAGS_quic_reloadable_flag_quic_fix_adaptive_time_loss, false)
 
 // In QUIC BBR, keep sending at the max bandwidth observed in the previous 2
 // RTTs for another SRTT.
 QUIC_FLAG(bool,
           FLAGS_quic_reloadable_flag_quic_bbr_keep_sending_at_recent_rate,
           false)
 
 // Base CWND on SRTT instead of min_rtt for QUIC BBR.
 QUIC_FLAG(bool, FLAGS_quic_reloadable_flag_quic_bbr_base_cwnd_on_srtt, false)