### 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)


uint64_t last_scene_shadow_pass = light_storage->light_instance_get_shadow_pass(p_light);
		if (last_scene_shadow_pass != get_scene_pass()) {
			light_storage->light_instance_set_directional_rect(p_light, light_storage->get_directional_shadow_rect());
			light_storage->directional_shadow_increase_current_light();
			light_storage->light_instance_set_shadow_pass(p_light, get_scene_pass());
		}
		use_pancake = light_storage->light_get_param(base, RS::LIGHT_PARAM_SHADOW_PANCAKE_SIZE) > 0;
		light_projection = light_storage->light_instance_get_shadow_camera(p_light, p_pass);
		light_transform = light_storage->light_instance_get_shadow_transform(p_light, p_pass);
		atlas_rect = light_storage->light_instance_get_directional_rect(p_light);
		if (light_storage->light_directional_get_shadow_mode(base) == RS::LIGHT_DIRECTIONAL_SHADOW_PARALLEL_4_SPLITS) {
			atlas_rect.size.width /= 2;
			atlas_rect.size.height /= 2;
			if (p_pass == 1) {
				atlas_rect.position.x += atlas_rect.size.width;
			} else if (p_pass == 2) {
				atlas_rect.position.y += atlas_rect.size.height;
			} else if (p_pass == 3) {
				atlas_rect.position += atlas_rect.size;
			}
		} else if (light_storage->light_directional_get_shadow_mode(base) == RS::LIGHT_DIRECTIONAL_SHADOW_PARALLEL_2_SPLITS) {
			atlas_rect.size.height /= 2;
			if (p_pass == 0) {
			} else {
				atlas_rect.position.y += atlas_rect.size.height;
			}
		}
		float directional_shadow_size = light_storage->directional_shadow_get_size();
		Rect2 atlas_rect_norm = atlas_rect;