### 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();
	ERR_FAIL_COND(!light_storage->owns_light_instance(p_light));
	RID base = light_storage->light_instance_get_base_light(p_light);
	Rect2i atlas_rect;
	uint32_t atlas_size = 1;
	RID atlas_fb;
	bool using_dual_paraboloid = false;
	bool using_dual_paraboloid_flip = false;
	Vector2i dual_paraboloid_offset;
	RID render_fb;
	RID render_texture;
	float zfar;
	bool use_pancake = false;
	bool render_cubemap = false;
	bool finalize_cubemap = false;
	bool flip_y = false;
	Projection light_projection;
	Transform3D light_transform;
	if (light_storage->light_get_type(base) == RS::LIGHT_DIRECTIONAL) {