Yes, you contributed to a ROTH 401k if it was through your paycheck so remove the contribution for the IRA in TurboTax Deductions & Credits section.
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It's actually likely that it's the designated Roth account in the federal TSP rather than in a 401(k), but the answer is the same. Neither a 401(k) nor the federal TSP is an IRA. Enter amounts shown in box 12 of your W-2 only in box 12 of TurboTax's W-2 form, nowhere else in TurboTax. Under Deductions & Credits, go back and remove the Roth IRA contribution that you did not actually make.