Bug 20495: Remove get_saved_report

Bug 20495: Remove get_saved_report

To test:
1 - prove t/db_dependent/Reports/Guided.t
2 - grep "get_saved_report" - ensure there are no occurences of the
singular form
3 - create, save, edit, and convert a report
4 - access a public report and report json from opac and staff client
5 - Ensure all function as expected

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>