gfe-relnote: use GetMinRtt to calculate lower bound of pacing rate when overshoot detected to avoid divided by 0 problem. Protected by existing gfe2_reloadable_flag_quic_bbr_mitigate_overly_large_bandwidth_sample. PiperOrigin-RevId: 294210302 Change-Id: I40b14a7be0d040aa29afb9224d7436b137f556d1