I would revisit the W-2 section to make sure there isn't an incomplete entry that is prompting this question.
1.) Federal Taxes
2.) Wages and Income
3.) I'll Choose What I Work On
4.) Click Update next to Wages and Salaries
4.) Click through the screens until you see a screen titled Here's your W-2 info
5.) Click Delete next to any W-2 entry that you wish to delete