Go back to the My Info section of your return to delete a dependent being claimed if the duplicate Social Security number belongs to a dependent.
Or, if the duplicate Social Security number is for you or your spouse, then you may need to file your return by mail.
See the following TurboTax help articles for more information:
How do I add or remove a dependent?
E-file rejections related to incorrect or duplicated names, birth dates, or Social Security numbers