If you'll click "Forms" mode in the upper right corner of TurboTax, you can pull up Form M1PR and delete it.
I found I had to delete the state return and start over, as mentioned in https://ttlc.intuit.com/community/tax-credits-deductions/discussion/please-remove-all-the-related-inputs-you-entered-after-ch/01/192898/highlight/true#M25486