gdk: revert surface activation change
c926b28d ('gdk: do not deactivate surface on keyboard grabs') and f23bfc6b ('gdk: activate surface on keyboard grabs') changed the situation where surfaces are considered active by gdk. This however has unwanted consequences in the behavior of gnome-shell which is not properly transferring focus for Orca to get the proper active events, see for instance gnome-shell#452
We'd thus just better these changes for now, until such issues are fixed.
See #85