doc/treefile.md: Document remove-files
doc/treefile.md: Document remove-files

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