Bug 7734: NO_LIBRARY_SET should be translatable

Bug 7734: NO_LIBRARY_SET should be translatable

To test:
- Make sure you are logged into Koha as 'root' user - not superlibrarian
- Before the patch the label will show 'NO_LIBRARY_SET', after applying
  the patch it will be 'NO LIBRARY SET' without underscores.
- Verify correct description is shown after selecting a library.

Signed-off-by: mveron <veron@veron.ch>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>