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 in TurboTax Online, select “Start a New Return” from under “My Returns” in the top 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 Trash Can 🗑 next to it or “Delete” under the return’s name.
When you create your new return, you can just not add the donation, if you added it yourself.