Downgrade a QUIC_BUG to QUIC_LOG(WARNING).
Downgrade a QUIC_BUG to QUIC_LOG(WARNING).

gfe-relnote: n/a (log only change)
PiperOrigin-RevId: 268228941
Change-Id: Ie566a6050bb120d779c3cdcc43d1555078550515

google/quiche,google/quiche,google/quiche,google/quiche