flocke [1] filed a deletion request for arc-themes [2]:
https://aur.archlinux.org/packages/gtk-theme-arc/ provides the same Gtk theme. I must have overlooked it before creating this one.
[1] https://aur.archlinux.org/account/flocke/ [2] https://aur.archlinux.org/pkgbase/arc-themes/
Request #5190 has been accepted by flocke [1]:
Deletion of a fresh package requested by its current maintainer.
aur-requests@lists.archlinux.org