"While filling out my 2022 tax forms, TurboTax prompted me to file an amendment for 2021"
This is simply a reminder that your 2021 tax return should have reflected the fact that excess contribution was returned before the due date of the 2021 tax return. Your 2021 tax return already reflects that by the fact that it included no Form 5329 and that there were no taxable gains attributable to the $6,000 contribution that was returned (because there was instead a loss which is not reportable). (Your 2021 tax return should also have included an explanation statement regarding the return of contribution. If it didn't you can just provide explanation if and when the IRS questions the excess Roth IRA contribution.)
Because you properly corrected the excess contribution before the due date of your 2021 tax return, you have no excess contribution carried into 2022 to enter into 2022 TurboTax.
