### 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)


}
	bool render_shadows = p_render_data->directional_shadows.size() || p_render_data->shadows.size();
	
	if (render_shadows) {
		RENDER_TIMESTAMP("Render Shadows");
		_render_shadow_begin();
		
		for (uint32_t i = 0; i < p_render_data->directional_shadows.size(); i++) {
			_render_shadow_pass(p_render_data->render_shadows[p_render_data->directional_shadows[i]].light, p_render_data->shadow_atlas, p_render_data->render_shadows[p_render_data->directional_shadows[i]].pass, p_render_data->render_shadows[p_render_data->directional_shadows[i]].instances, camera_plane, lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, false, i == p_render_data->directional_shadows.size() - 1, false, p_render_data->render_info);
		}
		
		for (uint32_t i = 0; i < p_render_data->shadows.size(); i++) {
			_render_shadow_pass(p_render_data->render_shadows[p_render_data->shadows[i]].light, p_render_data->shadow_atlas, p_render_data->render_shadows[p_render_data->shadows[i]].pass, p_render_data->render_shadows[p_render_data->shadows[i]].instances, camera_plane, lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, i == 0, i == p_render_data->shadows.size() - 1, true, p_render_data->render_info);
		}
		_render_shadow_process();
		_render_shadow_end(RD::BARRIER_MASK_NO_BARRIER);
	}
	
	RD::get_singleton()->barrier(RD::BARRIER_MASK_ALL_BARRIERS, RD::BARRIER_MASK_ALL_BARRIERS);
	bool using_shadows = true;
	if (p_render_data->reflection_probe.is_valid()) {
		if (!RSG::light_storage->reflection_probe_renders_shadows(light_storage->reflection_probe_instance_get_probe(p_render_data->reflection_probe))) {
			using_shadows = false;
		}
	} else {
		
		light_storage->update_reflection_probe_buffer(p_render_data, *p_render_data->reflection_probes, p_render_data->scene_data->cam_transform.affine_inverse(), p_render_data->environment);
	}
	uint32_t directional_light_count = 0;
	uint32_t positional_light_count = 0;