Update screenshots for importing models

[pjmonks]

Due to changes made to the importer UI in MauroDataMapper/mdm-ui#605, some screenshots of the import process may need to be updated. One specific example I've found is here: https://maurodatamapper.github.io/user-guides/import-data-model-from-excel/import-data-model-from-excel/#2-import-data-model