Deprecate gfe2_reloadable_flag_quic_bbr2_lower_startup_cwnd_gain.

PiperOrigin-RevId: 312130631
Change-Id: I1f3556b68c9d3eb1b4af4389a794df73fe876f12

quic/core/congestion_control/bbr2_sender.cc

diff --git a/quic/core/congestion_control/bbr2_sender.cc b/quic/core/congestion_control/bbr2_sender.cc
index 8c0171b..8c3f7e5 100644
--- a/quic/core/congestion_control/bbr2_sender.cc
+++ b/quic/core/congestion_control/bbr2_sender.cc
@@ -133,8 +133,7 @@
 
 void Bbr2Sender::ApplyConnectionOptions(
     const QuicTagVector& connection_options) {
-  if (GetQuicReloadableFlag(quic_bbr2_lower_startup_cwnd_gain) &&
-      ContainsQuicTag(connection_options, kBBQ2)) {
+  if (ContainsQuicTag(connection_options, kBBQ2)) {
     // 2 is the lower, derived gain for CWND.
     params_.startup_cwnd_gain = 2;
     params_.drain_cwnd_gain = 2;