Update tracker TOML configuration (breaking changes)

After merging this [PR](https://github.com/torrust/torrust-tracker/pull/897), the tracker's TOML configuration will change. For a list of changes, see this [issue](https://github.com/torrust/torrust-tracker/issues/878).