
ControlsLayout is a tiny layout manager whose only purpose
is emit "allocation-changed" after allocation. This signal
was listened to update the workspaces actual geometry.
However, since d66cd0d206
, ControlsManager doesn't listen
to this signal anymore, rendering the class useless.
Remove ControlsLayout.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1518>