### 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)


uint32_t shadow_pass_index = scene_state.shadow_passes.size();
	SceneState::ShadowPass shadow_pass;
	if (p_render_info) {
		p_render_info->info[RS::VIEWPORT_RENDER_INFO_TYPE_SHADOW][RS::VIEWPORT_RENDER_INFO_DRAW_CALLS_IN_FRAME] = p_instances.size();
		p_render_info->info[RS::VIEWPORT_RENDER_INFO_TYPE_SHADOW][RS::VIEWPORT_RENDER_INFO_OBJECTS_IN_FRAME] = p_instances.size();
	}
	RenderSceneDataRD scene_data;
	scene_data.cam_projection = p_projection;
	scene_data.cam_transform = p_transform;
	scene_data.view_projection[0] = p_projection;
	scene_data.z_near = 0.0;
	scene_data.z_far = p_zfar;
	scene_data.lod_distance_multiplier = p_lod_distance_multiplier;
	scene_data.dual_paraboloid_side = p_use_dp_flip ? -1 : 1;
	scene_data.opaque_prepass_threshold = 0.1;
	scene_data.time = time;
	scene_data.time_step = time_step;
	RenderDataRD render_data;
	render_data.scene_data = &scene_data;
	render_data.instances = &p_instances;
	render_data.render_info = p_render_info;
	_setup_environment(&render_data, true, Vector2(1, 1), !p_flip_y, Color(), false, p_use_pancake, shadow_pass_index);
	if (get_debug_draw_mode() == RS::VIEWPORT_DEBUG_DRAW_DISABLE_LOD) {
		scene_data.screen_mesh_lod_threshold = 0.0;
	} else {