Cleaning up removed registration fields

We’ve made a few changes to a registration form after registrants have been added. The user’s registration page shows a bunch of entries with “This field no longer exists”, which is great when those fields actually have data that should be retained. However, these fields are all blank for us because we changed it at a time where nobody had made changes.

It looks pretty messy right now, because there are e.g. two T-Shirt fields because we moved it between sections by removing and adding.

Is there a way to cleanse these fields, so they no longer show up in the registration?