treecompose: Remove code to delete cached packages
treecompose: Remove code to delete cached packages

No longer needed now that we recommend an HTTP proxy.

mdshuai/rpm-ostree,cgwalters/rpm-ostree-cgwalters,mdshuai/rpm-ostree,cgwalters/rpm-ostree-cgwalters,mdshuai/rpm-ostree,tmp-user/rpm-ostree,giuseppe/rpm-ostree,mdshuai/rpm-ostree,giuseppe/rpm-ostree,giuseppe/rpm-ostree,tmp-user/rpm-ostree,tmp-user/rpm-ostree,tmp-user/rpm-ostree,giuseppe/rpm-ostree,cgwalters/rpm-ostree-cgwalters