windowManager: Remove four finger app switch gesture

This gesture is not implemented very well, it's basically a hack. It
also doesn't work all the time and using it sometimes leaves the shell
in a broken state.

GNOME/gnome-shell!380
1 job for remove-four-finger-appswitch in 1 minute and 32 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Source Check
passed #202452
js_check

00:01:32