Version 4.0.0 of ml-app-deployer [removed AppConfig's `getConfigDir` method](https://github.com/marklogic-community/ml-app-deployer/commit/f1a03e93f54b966efa1354d974d522297887db35#diff-1eea7992acd9827623a9292c3add8583L622) (replaced by `getConfigDirs`. `ExportResourcesTask` (called by `mlExportResources`) [still refers to it](https://github.com/marklogic-community/ml-gradle/blob/3ce91d25eaeb579f1daac335106aa82855047fc8/src/main/groovy/com/marklogic/gradle/task/export/ExportResourcesTask.groovy#L53).