TurboTax online account cannot be deleted.  You can remove any tax data entered for 2019 if you have not filed or paid the account fees.

If you have not paid for the online edition you are using, have not filed your tax return or registered the Free edition, then you can clear your return. Click on Tax Tools on the left side of the program screen while working on the 2019 online tax return. Click on Clear & Start Over.