Yes, you can disregard it. The amended return doesn't go anywhere if you don't mail it.
BUT - When you start your 2019 tax return, TurboTax is going to transfer your 2018 information from the amended return, not the original 2018 return that you actually filed. Also, if you download your 2018 tax return for any reason, you are going to get the amended return, not your original return. For these reasons, you might want to go back into TurboTax and change your 2018 return back to the way it was when you filed it.
The FAQ at the link below gives instructions for canceling an amended return in TurboTax Online. But I think that will just remove the Form 1040X. I don't think it will undo the changes that you made.
https://ttlc.intuit.com/questions/2552802-how-do-i-cancel-or-undo-an-amended-return-in-turbotax-onli...
