Replace QUIC_VERSION_99 with QUIC_VERSION_IETF_DRAFT_27 Now that IETF drafts do not change as quickly, we no longer need a dumping ground for changes, so we're retiring QUIC_VERSION_99. The same functionality is now taken over by QUIC_VERSION_IETF_DRAFT_27. gfe-relnote: no behavior change, protected by quic_enable_version_draft_27 PiperOrigin-RevId: 299195934 Change-Id: Ic5c7769574c1569edca3c31f1e05d867f7a5c29a