Fix issues with Alfred's preferences syncing

This PR addresses #7216.

In case a custom Alfred syncing directory is used, you will get the following error if you try to link Alfred:
`Alfred 2.4+ detected, but local preferences file not found. Try running Alfred first.`

`LOCALPREFS_SCOPES_FILEGLOB` has been replaced with a method that looks up `syncfolder` in Alfred's preferences.