You can't do that from within Paratext, but it should be easy externally.
You need to navigate to your My Paratext Projects folder, then the folder for that project. Inside that folder there will be a file called TermRenderings.xml
Open that with your favorite text editor (Notepad, Wordpad, etc., but not something like Microsoft Word), make the replacement, and save it. Then test to see if it did what you expected. You'll want to make the edit while PT is closed, and then turn it on after you've saved.
As normal when doing edits externally, it's always a good practice to back up the file before you edit in case you do something wrong.