When you opened your 2020 return, you were probably asked if you wanted to import your tax information from 2019 (assuming that you did your 2019 taxes with TurboTax). If you said "yes", then certain things were carried over, like your W-2.
However, only the name of your employer, address, and the like is carried over - the dollar amounts are not, because you need to enter the new dollar amounts for 2020.
If, however, you didn't work for that employer in 2020, then you will need to delete this W-2.
To do so, please do a Search (upper right) for w-2 and click on the jump-to link (Mac users must find the W-2 in the Topics List). This should show you a table of W-2 that are entered. Once you identify the W-2 that you don't need any longer, use the Delete button or the trash can icon to get rid of it.