I had the same problem. I couldn't delete the Safe Harbor statement in Forms view (it just kept reappearing). So I went back to the beginning of the Rental Property section and clicked through the info, income, and expense questions for the property, and right at the end, after it looked like it was all done, the Safe Harbor question screen appeared and I was able to deselect the option. Hope this works for you!
Ps. On the separate "Is this Qualified Business Income?" screen, you can still select Yes there if your rental activity meets the definition shown ("based in the U.S. and carried on with regularity, continuity, and a profit motive"), which most ordinary rental businesses would.
