I know i am late responding to this query, but what you can do is, pick the scene7id stored in aem for the asset,
@Reference
private Scene7Service s7Service;
Scene7Asset scene7Asset = s7Service.getAssets(new String[]{scene7ID}, null, null, config).get(0);
s7Service.deleteAsset(scene7ID, config); // Deletes the asset with the "-AVS"
Let me know if you have any question. I have implemented this as a workflow step