Fix FileEditForm test usage
Fix FileEditForm test usage

Regression from https://github.com/silverstripe/silverstripe-asset-admin/commit/315cc652184880c64db704664538aa044c7901b4

silverstripe/silverstripe-asset-admin,open-sausages/silverstripe-asset-admin,open-sausages/silverstripe-assets-gallery,silverstripe/silverstripe-asset-admin,open-sausages/silverstripe-assets-gallery,open-sausages/silverstripe-asset-admin