In your VC dashboard, you are able to cancel a deal up until the point the SPV is finalized. In the "settings" tab of the specific deal, scroll down to the bottom of the page. You will see the below "delete" button.

Deleting the deal will completely remove the opportunity from your dashboard and all LPs will no longer have access. If you do not see a delete button, this means that your SPV has already been finalized.