### 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)


} else if (p_render_list == RENDER_LIST_SECONDARY) { 
						p_render_data->render_info->info[RS::VIEWPORT_RENDER_INFO_TYPE_SHADOW][RS::VIEWPORT_RENDER_INFO_PRIMITIVES_IN_FRAME] += indices;
					}
				}
			} else {
				surf->lod_index = 0;
				if (p_render_data->render_info) {
					uint32_t to_draw = mesh_storage->mesh_surface_get_vertices_drawn_count(surf->surface);
					to_draw = _indices_to_primitives(surf->primitive, to_draw);
					to_draw *= inst->instance_count;
					if (p_render_list == RENDER_LIST_OPAQUE) { 
						p_render_data->render_info->info[RS::VIEWPORT_RENDER_INFO_TYPE_VISIBLE][RS::VIEWPORT_RENDER_INFO_PRIMITIVES_IN_FRAME] += to_draw;
					} else if (p_render_list == RENDER_LIST_SECONDARY) { 
						p_render_data->render_info->info[RS::VIEWPORT_RENDER_INFO_TYPE_SHADOW][RS::VIEWPORT_RENDER_INFO_PRIMITIVES_IN_FRAME] += to_draw;
					}
				}
			}
			
			if (p_pass_mode == PASS_MODE_COLOR || p_pass_mode == PASS_MODE_COLOR_TRANSPARENT) {
#ifdef DEBUG_ENABLED
				bool force_alpha = unlikely(get_debug_draw_mode() == RS::VIEWPORT_DEBUG_DRAW_OVERDRAW);
#else
				bool force_alpha = false;
#endif
				if (!force_alpha && (surf->flags & GeometryInstanceSurfaceDataCache::FLAG_PASS_OPAQUE)) {
					rl->add_element(surf);
				}
				if (force_alpha || (surf->flags & GeometryInstanceSurfaceDataCache::FLAG_PASS_ALPHA)) {
					render_list[RENDER_LIST_ALPHA].add_element(surf);
				}