gfe-relnote: In QUIC, default enable IETF loss detection with 1/4 RTT time threshold and adaptive packet threshold. Protected by existing gfe2_reloadable_flag_quic_default_on_ietf_loss_detection. PiperOrigin-RevId: 284345000 Change-Id: I83071dae7ac6c0e2598d23fe555716c26bc9730e