Remove elements to prefix /etc to /usr/etc
There was a comment in https://gitlab.gnome.org/GNOME/gnome-build-meta/merge_requests/162 that this is now automatically done through flatpak-image plugin.
There was a comment in https://gitlab.gnome.org/GNOME/gnome-build-meta/merge_requests/162 that this is now automatically done through flatpak-image plugin.