### 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()) {
					RID dest_framebuffer = rb_data->get_color_fbs(RenderBufferDataForwardMobile::FB_CONFIG_ONE_PASS);
					RID texture = RendererRD::TextureStorage::get_singleton()->render_target_get_rd_texture(rb->get_render_target());
					copy_effects->copy_to_fb_rect(texture, dest_framebuffer, Rect2i(), false, false, false, false, RID(), false, false, true);
				}
				keep_color = true;
			} break;
			case RS::ENV_BG_KEEP: {
				keep_color = true;
			} break;
			case RS::ENV_BG_CAMERA_FEED: {
			} break;
			default: {
			}
		}
		
		if (draw_sky || draw_sky_fog_only || environment_get_reflection_source(p_render_data->environment) == RS::ENV_REFLECTION_SOURCE_SKY || environment_get_ambient_source(p_render_data->environment) == RS::ENV_AMBIENT_SOURCE_SKY) {
			RENDER_TIMESTAMP("Setup Sky");
			RD::get_singleton()->draw_command_begin_label("Setup Sky");
			
			if (is_reflection_probe) {
				Vector3 eye_offset;
				Projection correction;
				correction.set_depth_correction(true);
				Projection projection = correction * p_render_data->scene_data->cam_projection;
				sky.setup_sky(p_render_data->environment, p_render_data->render_buffers, *p_render_data->lights, p_render_data->camera_attributes, 1, &projection, &eye_offset, p_render_data->scene_data->cam_transform, projection, screen_size, this);
			} else {
				sky.setup_sky(p_render_data->environment, p_render_data->render_buffers, *p_render_data->lights, p_render_data->camera_attributes, p_render_data->scene_data->view_count, p_render_data->scene_data->view_projection, p_render_data->scene_data->view_eye_offset, p_render_data->scene_data->cam_transform, p_render_data->scene_data->cam_projection, screen_size, this);
			}
			sky_energy_multiplier *= bg_energy_multiplier;