### Godot version

4.0 Stable

### System information

Ubuntu 22.04

### Issue description

Setting fog_affect_sky = 1 do not have the desired effect when using a Color sky mode. It works properly if we use a procedural sky or the forward+ renderer.

![Screenshot from 2023-03-03 16-50-53](https://user-images.githubusercontent.com/8985409/222870514-0195c4cb-bbca-4e9b-bb6a-6e2a568d2f7b.png)


### Steps to reproduce

Add a sky with a plain color mode like the Clear Color default option. Enable fog and set fog_affect_sky value to 1. Sky is still not affected by fog. 

### Minimal reproduction project
[mobile_fog_sky_bug.zip](https://github.com/godotengine/godot/files/10887265/mobile_fog_sky_bug.zip)


while (geometry_instance_dirty_list.first()) {
		_geometry_instance_update(geometry_instance_dirty_list.first()->self());
	}
}
void RenderForwardMobile::_geometry_instance_dependency_changed(Dependency::DependencyChangedNotification p_notification, DependencyTracker *p_tracker) {
	switch (p_notification) {
		case Dependency::DEPENDENCY_CHANGED_MATERIAL:
		case Dependency::DEPENDENCY_CHANGED_MESH:
		case Dependency::DEPENDENCY_CHANGED_PARTICLES:
		case Dependency::DEPENDENCY_CHANGED_MULTIMESH:
		case Dependency::DEPENDENCY_CHANGED_SKELETON_DATA: {
			static_cast<RenderGeometryInstance *>(p_tracker->userdata)->_mark_dirty();
			static_cast<GeometryInstanceForwardMobile *>(p_tracker->userdata)->data->dirty_dependencies = true;
		} break;
		case Dependency::DEPENDENCY_CHANGED_MULTIMESH_VISIBLE_INSTANCES: {
			GeometryInstanceForwardMobile *ginstance = static_cast<GeometryInstanceForwardMobile *>(p_tracker->userdata);
			if (ginstance->data->base_type == RS::INSTANCE_MULTIMESH) {
				ginstance->instance_count = RendererRD::MeshStorage::get_singleton()->multimesh_get_instances_to_draw(ginstance->data->base);
			}
		} break;
		default: {
			
		} break;
	}
}
void RenderForwardMobile::_geometry_instance_dependency_deleted(const RID &p_dependency, DependencyTracker *p_tracker) {