Remove oauth_integrations app

[millerdev]

Removes an unused app developed for Google Sheets integration, which was never released. The main motivation for this is to remove the dependencies that it added. If we add Gsheets integration in the future we should consider using oauth libraries that we use elsewhere to minimize the number of dependencies we need to maintain.

Safety Assurance

Safety story

Nothing references this app. The /oauth/google_sheets_* URL patterns have not been hit on production for over 2 months.

Automated test coverage

No.

Migrations

• The migrations in this code can be safely applied first independently of the code since the code is not being used (there would be 500 errors if the removed URL patterns were accessed).

Rollback instructions

• A reverse migration will need to be developed if we want to revert this PR.

[millerdev]

Closing since it sounds like some of this may be useful after all.

[millerdev]

google-auth-oauthlib upgraded by #33873