This commit removes fetches of ostree-metadata from
flatpak_dir_install() and flatpak_dir_update(), which both pull it into
the child repo when doing system-helper deployments. Both functions have
a FlatpakRemoteState object passed in and when that is initialized,
_flatpak_dir_fetch_remote_state_metadata_branch() pulls and deploys
ostree-metadata so it can be queried against for repo metadata and
served onto LAN and USB peers. So there's no need to pull it again here.
The issue of resolving a ref and its metadata atomically remains, but
that will be addressed by https://github.com/flatpak/flatpak/pull/1796.
Closes: #1806
Approved by: alexlarsson
4e73b51a0b