displayio: Set in_group to false when removing a layer from a group

Otherwise the removed layer cannot be re-added.

Author: deshipu

shared-module/displayio/Group.c

@@ -310,13 +310,15 @@ static void _remove_layer(displayio_group_t *self, size_t index) {
         self->members->items[index], &displayio_tilegrid_type);
     if (layer != MP_OBJ_NULL) {
         displayio_tilegrid_t *tilegrid = layer;
+        tilegrid->in_group = false;
         rendered_last_frame = displayio_tilegrid_get_previous_area(tilegrid, &layer_area);
         displayio_tilegrid_update_transform(tilegrid, NULL);
     }
     layer = mp_obj_cast_to_native_base(
         self->members->items[index], &displayio_group_type);
     if (layer != MP_OBJ_NULL) {
         displayio_group_t *group = layer;
+        group->in_group = false;
         rendered_last_frame = displayio_group_get_previous_area(group, &layer_area);
         displayio_group_update_transform(group, NULL);
     }