Varnish should not be included in the relationships

When using Platformify in a project and including Varnish in the application services, the following relationship is created:

```yaml
varnish: "varnish:varnish"
```

Varnish relationship should be the opposite one, linking from Varnish to the app.
[Docs reference](https://docs.upsun.com/add-services/varnish.html#1-configure-the-service)