gfe-relnote: n/a (logging only change)
gfe-relnote: n/a (logging only change)

Downgrade a WARNING log to DLOG.

PiperOrigin-RevId: 273303930
Change-Id: Ib6aa96977d0bbba0d3424e76b79055b73d0a4b37

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