The migration from GdkScreen's monitor API to GdkMonitor left out a way
to get the connector's name of a monitor.
While there's no real guarantee coming from the underlying graphics
system that the connector's name is stable, some system components may
use it to uniquely identify a monitor until the next plug in/out event.
Remove all the old 2.x and 3.x version annotations.
GTK+ 4 is a new start, and from the perspective of a
GTK+ 4 developer all these APIs have been around since
the beginning.
