xwayland: remove wl_log_set_handler_client workaround
This bumps the minimum Wayland version to 1.5 (released in 2014). Signed-off-by: Simon Ser <contact@emersion.fr> Reviewed-by: Michel Dänzer <mdaenzer@redhat.com> Reviewed-by: Olivier Fourdan <ofourdan@redhat.com> Reviewed-by: Martin Peres <martin.peres@mupuf.org>