authz: disable p4 repo-centric sync with sub-repo perms
Created by: bobheadxi
This allows us to safely assume that we will not accidentally grant access to a repo before sub-repo permissions are sync'd via user-centric sync.
In the long term we might want to implement sub-repo perms for repo-centric sync, but for now this is more straight-forward.
Related to #26644 (closed)