Unfortunately, the software doesn't allow that credit unless you upgrade.
To get rid of it....so you can stay in the "Free" version, go thru Retirement Savings Credit interview again, and indicate you were a student during 2020...that will get rid of it.
IF you later have some other tax situation, that ends up requiring you to upgrade anyhow, you can go thru that part of the interview and say No to the student question to get it back.
The Saver's Credit is a 'non-refundable' credit. That means this credit can reduce the tax you owe to zero, but it can't provide you with a tax refund.
To remove the credit :
You won't qualify for the credit if you check that you were a full time student.