You can delete your state return in TurboTax Online as long as you haven't paid or registered yet. Check your W-2 or other tax forms where you entered MI state withholding and correct the entry. 

If you haven't paid for TurboTax and need to delete the state:

1. Sign in and open your return if you don't already have it open.
2. From the left-side menu, select State (select the menu icon in the upper-left if you don't see this) and then select Continue on the Let's get your state taxes done right screen.
3. On the following screen, Status of your state returns, select Delete to the right of your state, then answer Yes.

If you don't see the option to delete your state, it means you already paid your TurboTax fees (which includes the state fee) or registered your free version while the state was still on your return.