Documentation describes Great Deluge config option that does not exist

The Great Deluge section (https://docs.optaplanner.org/latestFinal/optaplanner-docs/html_single/index.html#greatDeluge)

speaks about an option that effectively does not exist, as it has been commented out in the optaplanner-core:

greatDelugeInitialWaterLevel

We should either enable that config option if it's worth it or update the docs.