gesture: fix Hover by handling pointer.Cancel event

pointer.Cancel event is ignored, resulting in Hovered returning true
even though the pointer is no longer hovering over the region.
This change fixes it.

Signed-off-by: Rajiv Kanchan <rajiivkanchan@gmail.com>

gesture/gesture.go

@@ -51,7 +51,7 @@ func (h *Hover) Hovered(q event.Queue) bool {
 			continue
 		}
 		switch e.Type {
-		case pointer.Leave:
+		case pointer.Leave, pointer.Cancel:
 			if h.entered && h.pid == e.PointerID {
 				h.entered = false
 			}