wayland: remove bogus xdg_activation_token_v1_set_surface()
xdg_activation_token_v1_set_surface() is used to set the source surface, ie. the surface where the focus currently is.
GTK instead passes the surface it wants to activate. This is incorrect and makes wlroots reject the activation.
See https://github.com/swaywm/sway/issues/4155#issuecomment-1329799126
cc @jadahl