Here are my best guesses. Don't quote me unless I am right. 

Only guessing - Settings > Options > Firm Info > I think you may see both listed in the Firm box down to the left. POSSIBLY you can delete one there?

This tells how to install, but not remove https://proconnect.intuit.com/community/help-articles/help/installing-multiple-firms-or-preparer-fil...

My other guess is that there are two files in Lacerte/20tax/OPTION20 that look slightly different

My last guess is to exit the program and rename Lacerte/20tax/OPTION20/Firms.w0 to Lacerte/20tax/OPTION20/Firms.old

Enter the program and probably get an error, then go to settings and download the prep file you want.