I don’t know what dll.airtable is, but currently, attachment URLs never expire and there is no way to inactivate them.
This behavior will change in the future, but there is no timeline for this behavior change.
You might want to email email@example.com to see if they can manually inactivate an attachment URL for you. I don’t know if they can, but it’s worth a try.
It’s the domain for the CDN Airtable uses for attachment hosting.
One approach - issue a DMCA takedown notice to Airtable. They would have no option except to comply and this should be your last resort. But this avenue would be especially helpful if you inadvertently exposed some sensitive data without fully realizing their platform’s shortcomings.