Fix FreeMarker startup warning

After the last FreeMarker library upgrade from 2.3.29 to 2.3.30 (NXP-29792) we now have a warning at startup in the console:

SEVERE: DefaultObjectWrapper.incompatibleImprovements was set to the object returned by Configuration.getVersion(). That defeats the purpose of incompatibleImprovements, and makes upgrading FreeMarker a potentially breaking change. Also, this probably won't be allowed starting from 2.4.0. Instead, set incompatibleImprovements to the highest concrete version that's known to be compatible with your application.