widget: Cancel also denied sequences

It makes no sense to skip denied sequences here, the gestures are
still carrying out the accounting for these, which must be also put
to an end if we're possibly not receiving any further events from
this sequence.

https://bugzilla.gnome.org/show_bug.cgi?id=754098

gtk/gtkwidget.c

@@ -4294,9 +4294,6 @@ _gtk_widget_cancel_sequence (GtkWidget        *widget,
           !gtk_gesture_handles_sequence (gesture, seq))
         seq = NULL;
 
-      if (!gtk_gesture_handles_sequence (gesture, seq))
-        continue;
-
       handled |= _gtk_gesture_cancel_sequence (gesture, seq);
     }