gfe-relnote: n/a(clean up) Switch existing directly access of FLAGS to use GetQuicFlag.
gfe-relnote: n/a(clean up) Switch existing directly access of FLAGS to use
GetQuicFlag.

PiperOrigin-RevId: 253024482
Change-Id: I191413c821c8e91a15e9fce6ac36bb94e1a87ccf

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