### 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)


texture = texture_storage->texture_rd_get_default(RendererRD::TextureStorage::DEFAULT_RD_TEXTURE_DEPTH);
		}
		u.append_id(texture);
		uniforms.push_back(u);
	}
	{
		RD::Uniform u;
		u.binding = 10;
		u.uniform_type = RD::UNIFORM_TYPE_TEXTURE;
		RID texture = rb_data.is_valid() ? rb->get_back_buffer_texture() : RID();
		if (texture.is_null()) {
			if (is_multiview) {
				texture = texture_storage->texture_rd_get_default(RendererRD::TextureStorage::DEFAULT_RD_TEXTURE_2D_ARRAY_DEPTH);
			} else {
				texture = texture_storage->texture_rd_get_default(RendererRD::TextureStorage::DEFAULT_RD_TEXTURE_BLACK);
			}
		}
		u.append_id(texture);
		uniforms.push_back(u);
	}
	if (p_index >= (int)render_pass_uniform_sets.size()) {
		render_pass_uniform_sets.resize(p_index + 1);
	}
	if (render_pass_uniform_sets[p_index].is_valid() && RD::get_singleton()->uniform_set_is_valid(render_pass_uniform_sets[p_index])) {
		RD::get_singleton()->free(render_pass_uniform_sets[p_index]);
	}
	render_pass_uniform_sets[p_index] = RD::get_singleton()->uniform_set_create(uniforms, scene_shader.default_shader_rd, RENDER_PASS_UNIFORM_SET);
	return render_pass_uniform_sets[p_index];
}
void RenderForwardMobile::_setup_lightmaps(const RenderDataRD *p_render_data, const PagedArray<RID> &p_lightmaps, const Transform3D &p_cam_transform) {