gnome-shell now checks for an associated drive to automatically
cancel the operation on disconnect, so fake the corresponding
method. While at it, drop the `get_icon()` method that hasn't
been used for quite a while now.
Closes: https://gitlab.gnome.org/GNOME/gnome-shell-extensions/-/issues/508
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell-extensions/-/merge_requests/361>
(cherry picked from commit 8957f488dc)