Remove os.chmod() from RegistryContext initialization?

https://github.com/Subaru-PFS/obs_pfs/commit/cdc82a032b98eca51253622ccc1c23adad7b5c56 added a context manager for registry access. That does an os.chmod() on the registry itself. But chmod(2) requires that the process and file users match, not just the groups. So only the sqlite file owner can ingest files. [or someone in the group can exploit fragile hacks inside the directory. ]