Bug: Incorrect interpretation of GH internal repository visibility rules

Created by: abeatrix

Steps to reproduce:

1. Internal repos are synced to Sourcegraph, with permissions syncing enabled
2. Orgs members cannot search for them on Sourcegraph if they are not direct members of those internal repos

Expected behavior:

Internal repos are searchable even if org members do not have direct roles

Actual behavior:

Internal repos are not searchable for org members who do not have direct roles to those internal repos