2127222b39
It existed to fade out/in `nautilus-desktop` for the overview, but it only ever worked for X11 sessions (`Meta.WindowType.DESKTOP`) and `nautilus-desktop` no longer exists anyway. While I had suggested extending it in the past (!1395), that work was never finished and since then the DING extension has implemented its own visibility toggling. There seems little value in keeping the old fade logic around in gnome-shell. Removing it actually fixes a bug with DING (https://launchpad.net/bugs/1965072). Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2244>