You can file the directions in the TurboTax FAQ below to cancel your amendment:
https://ttlc.intuit.com/replies/4170678
Instructions on how to do it are provided in the following FAQ:
https://ttlc.intuit.com/community/amending/help/how-do-i-cancel-or-undo-an-amended-return-in-turbotax-online/00/26315