To remove a premium encryption key from a Template, open the Template that has been assigned the key.

You will be prompted to enter the Key to open the Template

Once the Template opens, scroll to the bottom,

Click on the 3 dots inside the Encryption Key tile

You will be prompted to Remove Link - Click on Remove Link

The Encryption Key is removed from the Template and the change is saved. The Template no longer shows the Encryption Key icon in the Vault directory.