Fix resize corners

I was stuck in an X session and noticed that my resize corners
all got east or north cursors. It turns out that gnome-shell
does not properly advertise support for edge constraints under X11,
and the absence of that makes the code for determining the edge
under the cursor misbehave.

This change should fix that.
4 jobs for fix-corner-resize in 14 minutes and 2 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #178830
fedora-x86_64

00:04:44

passed #178831
win32
msys2-mingw32

00:08:25

 
  Flatpak
passed #178832
flatpak:demo

00:05:36

passed #178833
flatpak:widget-factory

00:05:33