output-damage: drop unused pending_attach_render

include/wlr/types/wlr_output_damage.h

@@ -43,8 +43,6 @@ struct wlr_output_damage {
 	pixman_region32_t previous[WLR_OUTPUT_DAMAGE_PREVIOUS_LEN];
 	size_t previous_idx;
 
-	bool pending_attach_render;
-
 	struct {
 		struct wl_signal frame;
 		struct wl_signal destroy;