If you are preparing a return with your spouse/partner, you can't only add upgrades or extra features to one return. You would have to prepare your returns separately to apply audit protection to only one return.
Unfortunately, once you have upgraded or added features to your TurboTax return, there is no way to downgrade or remove the extra features. You would need to create a new return to go back to the original product.
To start a new return, select “Start a New Return” from under “My Returns” in the bottom left corner. Once you have started your new return, you can select “View All Returns” from under “My Returns”. Then delete the unwanted return by clicking the small Trash Can next to it or “Delete” under the return’s name.