Remove the event listener for "focus:" events
The focus:
event was deprecated years ago. But we've had to keep listening for these events mainly due to Gtk2 and Gtk3 sometimes failing to fire object:state-changed:focused
but continuing to fire focus:
.
We need to hunt down those issues and get them fixed in Gtk, at least in the case of Gtk3. Then we can finally stop listening for focus:
events.