gfe-relnote: Rename QuicSession::CryptoHandshakeEvent::HANDSHAKE_CONFIRMED to QuicSession::CryptoHandshakeEvent::EVENT_HANDSHAKE_CONFIRMED. Renaming only, not protected. PiperOrigin-RevId: 290302067 Change-Id: I7463e9f7281df68ee0fdf870db1daee1fd5f3cb4