On Windows, `app.update.auto` is now a per-installation pref stored in
C:\ProgramData\Zotero\Updates\[id]\update-config.json so that it can be
used by the background update service. We don't have a background update
service, so we force it to continue using the profile pref.
So a custom build doesn't have to modify each .ftl file
`app-name` is redundant with the Firefox strings, but it's what we used
previously and is easier to remember.
