Revert "workspacesView: Work around spurious allocation changes"

We now found the underlying bug: The ControlsManager (which causes the bad call to _updateWorkspacesFullGeometry()) is getting (re-)allocated while we add the view to the overviewGroup actor because the overviewGroup is already visible and the view is immediately getting mapped by clutter_actor_add_child_internal(). That causes a resource-scale calculation and that indirectly causes a call to _clutter_stage_maybe_relayout() (explained more detailed in the last commit).

So now that we got rid of the immediate relayout happening when mapping the view, we can revert this fix.

This reverts commit 6cc19ee6.

Depends on mutter!1181 (merged)