GNOME/gnome-control-center!387 ported info panel to use UDisks2 instead
of GUnixMounts and thus the helpers from gsd-disk-space-helper.[h|c] are
no more needed.
This panel was hidden in the new shell, and now that
we don't have the old one, can be safely dropped.
Minor adjustments were made to the other panels to
properly remove this panel.
https://bugzilla.gnome.org/show_bug.cgi?id=790923