### 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)


RendererRD::LightStorage *light_storage = RendererRD::LightStorage::get_singleton();
	RendererRD::TextureStorage *texture_storage = RendererRD::TextureStorage::get_singleton();
	p_render_data->cube_shadows.clear();
	p_render_data->shadows.clear();
	p_render_data->directional_shadows.clear();
	Plane camera_plane(-p_render_data->scene_data->cam_transform.basis.get_column(Vector3::AXIS_Z), p_render_data->scene_data->cam_transform.origin);
	float lod_distance_multiplier = p_render_data->scene_data->cam_projection.get_lod_multiplier();
	{
		for (int i = 0; i < p_render_data->render_shadow_count; i++) {
			RID li = p_render_data->render_shadows[i].light;
			RID base = light_storage->light_instance_get_base_light(li);
			if (light_storage->light_get_type(base) == RS::LIGHT_DIRECTIONAL) {
				p_render_data->directional_shadows.push_back(i);
			} else if (light_storage->light_get_type(base) == RS::LIGHT_OMNI && light_storage->light_omni_get_shadow_mode(base) == RS::LIGHT_OMNI_SHADOW_CUBE) {
				p_render_data->cube_shadows.push_back(i);
			} else {
				p_render_data->shadows.push_back(i);
			}
		}
		
		for (const int &index : p_render_data->cube_shadows) {
			_render_shadow_pass(p_render_data->render_shadows[index].light, p_render_data->shadow_atlas, p_render_data->render_shadows[index].pass, p_render_data->render_shadows[index].instances, camera_plane, lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, true, true, true, p_render_data->render_info);
		}
		if (p_render_data->directional_shadows.size()) {
			
			light_storage->update_directional_shadow_atlas();
			RD::get_singleton()->draw_list_begin(light_storage->direction_shadow_get_fb(), RD::INITIAL_ACTION_DROP, RD::FINAL_ACTION_DISCARD, RD::INITIAL_ACTION_CLEAR, RD::FINAL_ACTION_CONTINUE);
			RD::get_singleton()->draw_list_end();
		}