No such thing! The basis of the rate limit is that you've already expended the resources required for Let's Encrypt to create the certificate, deleting them isn't going to un-spend those resources.
You can evade this particular rate limit by creating a new certificate that has a second name on it.
For example, the certificate you created has just one name:
- dtn.plosz.ca
You can't create one like that anymore for another few days, due to the Duplicate Certificate Limit. But you could create a certiifcate that had a different set of names, as it would no longer count as a duplicate:
- dtn.plosz.ca
- www.dtn.plosz.ca