authz: bypass private repos without authz provider configured for the code host
Created by: unknwon
Previously, we had the following assumption (accidentally taken from working on explicit permissions APIs):
- When background permissions syncing is enabled, the site admin would want to enforce permissions for all repositories from all code hosts.
This PR removes this false assumption, and allows access to private repos that from code hosts which do not have authz provider configured.
Fixes #11318