Fix build for glib < 2.32
Fix build for glib < 2.32

G_SOURCE_REMOVE was introduced in 2.32

freedesktop-unofficial-mirror/spice__spice-gtk,SPICE/spice-gtk,Fantu/spice-gtk,guodong/spice-gtk,Fantu/spice-gtk,flexVDI/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,fgouget/spice-gtk,SPICE/spice-gtk,fgouget/spice-gtk,guodong/spice-gtk,Fantu/spice-gtk,elmarco/spice-gtk,elmarco/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,Fantu/spice-gtk,guodong/spice-gtk,SPICE/spice-gtk,elmarco/spice-gtk,elmarco/spice-gtk,guodong/spice-gtk,fgouget/spice-gtk,SPICE/spice-gtk,flexVDI/spice-gtk