You have a couple of options.
You can do a Full Import to sync your account with your work provider and this will update your items to only the open work orders. This article explains how to do this. > How To Refresh Your Work Orders From An Integration.
You could also go in on Pruvan.com and change the COMPLETED projects to CLOSED. This will also update the Projects list on your phone. Here is an article on how to do this. > How To Mass Update Your Pruvan Projects