Bug 17919: (bug 17466 follow-up) Koha::Issue is now called Koha::Checkout

Bug 17919: (bug 17466 follow-up) Koha::Issue is now called Koha::Checkout

Ignoring the pluralization or lack thereof:
$ git grep "Koha::Issue"
-- This has results.
But this was renamed by 17796, and supposedly still
in discussion in 16870.

apply this patch, and do the same git.
There will be no results.

This was found while running a prove t/db_dependent/00-strict.t

Signed-off-by: Claire Gravely <claire_gravely@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>