### 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)


}
	}
	{
		if (rb_data.is_valid()) {
			RD::get_singleton()->draw_command_begin_label("Render 3D Pass");
		} else {
			RD::get_singleton()->draw_command_begin_label("Render Reflection Probe Pass");
		}
		
		RD::get_singleton()->draw_command_begin_label("Render Opaque Subpass");
		p_render_data->scene_data->directional_light_count = p_render_data->directional_light_count;
		_setup_environment(p_render_data, is_reflection_probe, screen_size, !is_reflection_probe, p_default_bg_color, p_render_data->render_buffers.is_valid());
		if (using_subpass_transparent && using_subpass_post_process) {
			RENDER_TIMESTAMP("Render Opaque + Transparent + Tonemap");
		} else if (using_subpass_transparent) {
			RENDER_TIMESTAMP("Render Opaque + Transparent");
		} else {
			RENDER_TIMESTAMP("Render Opaque");
		}
		RID rp_uniform_set = _setup_render_pass_uniform_set(RENDER_LIST_OPAQUE, p_render_data, radiance_texture, true);
		bool can_continue_color = !using_subpass_transparent && !scene_state.used_screen_texture;
		bool can_continue_depth = !using_subpass_transparent && !scene_state.used_depth_texture;
		{
			
			Vector<Color> c;
			{
				Color cc = clear_color.srgb_to_linear();
				if (rb_data.is_valid()) {
					cc.a = 0; 
				}