Remove redundant database tables

There are some relics in the database from prior prototypes that can be removed.

We should **delete** the following tables:
- action_instance -- originally used with Ripple
- groups -- an initial auth list which was replaced with globus auth
- requests -- original task tracking that is no longer used
- results -- not used

Locate the schema or migration definitions and references for the action_instance, groups, requests, and results tables. Check whether any application code or tests still use them, then remove the obsolete table definitions and verify that the schema and relevant checks no longer include these tables.

Written by the indexing model from the issue text.