[Gtk3] GdkWin32: Remove klassTEMPSHADOW
As today shadows are drawn by GTK klassTEMPSHADOW is not needed anymore and only leads to broken rendering of menus.
Fixes issue #2019 (closed).
Edited by Luca Bacci
As today shadows are drawn by GTK klassTEMPSHADOW is not needed anymore and only leads to broken rendering of menus.
Fixes issue #2019 (closed).