I clicked through and found that this deduction wouldn't actually save me any money. I then couldn't find a way to get back to the free plan (they only charge you after you file, so this should be possible).
After struggling for a while, I called Turbotax support, which had me download screen-sharing software and kept telling me to press some button to cancel the paid plan, and it wouldn't work, telling me that it wasn't possible to switch back. He couldn't figure it out, couldn't switch it off on his end, and eventually told me I would have to create a new Turbotax account and start over.
Oh, and for the icing on the cake, he never stopped the screen-sharing session, and saw me input my SSN when I recreated my account. (Yes, I'm aware that I'm a fool for not closing it out myself, but I was really stressed, and it would've been professional to end the screen-sharing after we ended the call.)