Open up registry editor
Browse to: Computer\HKEY_CLASSES_ROOT\CLSID{018D5C66-4533-4307-9B53-224DE2ED1FE6}
Change the System.IsPinnedToNameSpaceTree from 1 to 0.
Close and open File Explorer, you will now find that the Personal OneDrive placeholder has gone and only your Business OneDrive placeholder (if you’re using Business OneDrive) is present.