### 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)


}
		uniforms.push_back(u);
	}
	
	{
		RD::Uniform u;
		u.binding = 6;
		u.uniform_type = RD::UNIFORM_TYPE_TEXTURE;
		RID default_tex = texture_storage->texture_rd_get_default(RendererRD::TextureStorage::DEFAULT_RD_TEXTURE_2D_ARRAY_WHITE);
		for (uint32_t i = 0; i < scene_state.max_lightmaps; i++) {
			if (p_render_data && i < p_render_data->lightmaps->size()) {
				RID base = light_storage->lightmap_instance_get_lightmap((*p_render_data->lightmaps)[i]);
				RID texture = light_storage->lightmap_get_texture(base);
				RID rd_texture = texture_storage->texture_get_rd_texture(texture);
				u.append_id(rd_texture);
			} else {
				u.append_id(default_tex);
			}
		}
		uniforms.push_back(u);
	}
	/*
	{
		RD::Uniform u;
		u.binding = 7;
		u.uniform_type = RD::UNIFORM_TYPE_TEXTURE;
		u.ids.resize(MAX_VOXEL_GI_INSTANCESS);
		RID default_tex = texture_storage->texture_rd_get_default(RendererRD::TextureStorage::DEFAULT_RD_TEXTURE_3D_WHITE);
		for (int i = 0; i < MAX_VOXEL_GI_INSTANCESS; i++) {
			if (i < (int)p_voxel_gi_instances.size()) {