appDisplay: Stop using toggle-mode with folder icons

appDisplay: Stop using toggle-mode with folder icons

This is essentially a left-over from the original folder design, dating
all the way back to commit 6e3e2d9 in 2013.

It no longer makes much sense with the current design iteration, where
we pretend that the icon pops out of the grid and becomes the dialog
(i.e. we hide the icon and zoom out the dialog from its position).

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/4114>
(cherry picked from commit e781d8155ab312a1335dd3082dfd8abfef8430b9)