dmg module doesn't embed a license

As clarified in the Discord discussion, a regression was introduced by this change in the dmg module:

The generated setting.json config for the dmgbuild Python module contains a key named build_license while it has to contain a license key instead.

My guess is that it was changed because after a recent update of the dmgbuild module, a build without a license was failing since the dmgbuild requires the license.licenses list to be not empty.