### 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)


p_render_data->scene_data->directional_light_count = 0;
	p_render_data->scene_data->opaque_prepass_threshold = 0.0;
	
	
	
	
	
	
	Size2i screen_size;
	RID framebuffer;
	bool reverse_cull = p_render_data->scene_data->cam_transform.basis.determinant() < 0;
	bool using_subpass_transparent = true;
	bool using_subpass_post_process = true;
	
	_fill_render_list(RENDER_LIST_OPAQUE, p_render_data, PASS_MODE_COLOR);
	render_list[RENDER_LIST_OPAQUE].sort_by_key();
	render_list[RENDER_LIST_ALPHA].sort_by_reverse_depth_and_priority();
	_fill_element_info(RENDER_LIST_OPAQUE);
	_fill_element_info(RENDER_LIST_ALPHA);
	if (p_render_data->render_info) {
		p_render_data->render_info->info[RS::VIEWPORT_RENDER_INFO_TYPE_VISIBLE][RS::VIEWPORT_RENDER_INFO_DRAW_CALLS_IN_FRAME] = p_render_data->instances->size();
		p_render_data->render_info->info[RS::VIEWPORT_RENDER_INFO_TYPE_VISIBLE][RS::VIEWPORT_RENDER_INFO_OBJECTS_IN_FRAME] = p_render_data->instances->size();
	}
	if (is_reflection_probe) {
		uint32_t resolution = light_storage->reflection_probe_instance_get_resolution(p_render_data->reflection_probe);
		screen_size.x = resolution;
		screen_size.y = resolution;
		framebuffer = light_storage->reflection_probe_instance_get_framebuffer(p_render_data->reflection_probe, p_render_data->reflection_probe_pass);
		if (light_storage->reflection_probe_is_interior(light_storage->reflection_probe_instance_get_probe(p_render_data->reflection_probe))) {
			p_render_data->environment = RID();