gfe-relnote: (n/a) Refactor Bbr2ProbeBwMode::OnCongestionEvent such that it only has one return point. No behavior change, not protected. This makes it easier to do things when bbr2 switches phases. PiperOrigin-RevId: 282350548 Change-Id: Ic94ccbf2328ba0c791a8162b096511889e317024