It depends. If you imported your information from a prior year and you had 1099 OID last year, it assumes you will have it again this year and hence included that form for you to complete. Another possibility is that even if you did not import information from last year, at the beginning of the return, TurboTax asks you some questions about the relevant tax forms which may be applicable to you and based on the questions you may have answered, a 1099 OID form was created for you.
If you feel you don't need a 1099 OID, please visit How do I view and delete forms in TurboTax Online for more information on how to delete forms in TurboTax.