nautilus-query-editor: Rename "[...] Not in Search Locations" to "[...] Not Indexed"

Using "Folder/Subfolders Not in Search Locations" has some problems:

• "Search Locations" isn't an easy recognizable term unless the user is familiarized with the Search Locations subpage from the Search panel of the Settings app. "Indexed", however, is a widely used term
• This can also be problematic to translate and the context may be lost

Before	After