2019 TurboTax is simply reminding you that the effect of your return of contribution needed to be reflected on your 2018 tax return.
Your 2018 tax return should have included an explanation statement for the return of contribution and TurboTax would have prompted you for that explanation if you had entered the 2019 Form 1099-R as if you had already received it. If you did that, you can ignore the 2019 Form 1099-R and 2019 TurboTax's reminder. If you did not do that and your 2018 tax return did not include this explanation statement, since there were no taxable gains you can either wait and see if the IRS detects what it thinks is an uncorrected excess contribution for 2018 and explain it at that time or file an amended 2018 tax return now that only serves to provide that explanation. There is no change in your 2018 tax liability if your 2018 tax return did not include a From 5329 reporting the excess contribution.
