We had a covenant on our property to do with the minimum size house that had to be built on the ppty. It didn't expire until later this year, but we sold our house with the covenant on the property. The house was already built and met the covenant requirements. You probably don't even need to bother to have it removed.
The removal of covenant is a document that can be lodged by the purchasers solicitor or bank with the other relevant documents (ie: discharge of mortgage, transfer of land, mortgage etc...)