Remove OrgStore and DatasetStore from ANDI

[christinepoydence]

What

Currently, organizations and datasets are being stored in two places in ANDI- Postgres and Redis. Only one strategy should be used for consistency. We should remove the storage in Redis of the organizations and datasets and exclusively use Postgres. This will involve removing the OrgStore and DatasetStore from ANDI and updating all locations where they are used with calls to Postgres to retrieve the orgs/datasets.