Upgrading MIMIC-IV on BigQuery

MIMIC-IV v3.0 is currently unavailable on BigQuery. Currently, the mimiciv_hosp and mimiciv_icu datasets on BigQuery contain MIMIC-IV v2.2, and access to these datasets is still available via PhysioNet by navigating to the v2.2 page. We plan to upgrade these BigQuery datasets in the near future, and will notify users when we do so.