I mistakenly got a retirement savings contribution credit but I did not get one. How do I remove the credit so I continue without upgrading.

The "Savers Credit" is triggered by an entry on your W-2. 

It's usually reported in Box 12 with code D. 

You can edit the Retirement Savings Contribution Credit (Form 8880)  interview under Deductions & Credits or type   saver's credit   into the search box

select YES to 'Did you make contributions in 2018?' and YES to 'Were you a full-time student?'

This will remove the credit.

You might also consider using IRS FREE FILE 

You might be able to file for free and get the credit, just be aware that if you want to switch to TurboTax in the future, you'll need to transfer your tax file from there. 

IRS FREE FILE