### 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)


}
void RenderForwardMobile::_render_particle_collider_heightfield(RID p_fb, const Transform3D &p_cam_transform, const Projection &p_cam_projection, const PagedArray<RenderGeometryInstance *> &p_instances) {
	RENDER_TIMESTAMP("Setup GPUParticlesCollisionHeightField3D");
	RD::get_singleton()->draw_command_begin_label("Render Collider Heightfield");
	_update_render_base_uniform_set();
	RenderSceneDataRD scene_data;
	scene_data.cam_projection = p_cam_projection;
	scene_data.cam_transform = p_cam_transform;
	scene_data.view_projection[0] = p_cam_projection;