Bug 27154: Remove Koha::Util::SystemPreferences

Bug 27154: Remove Koha::Util::SystemPreferences

On bug 15494, the same method "get_yaml_pref_hash" has been added to two modules,
Koha/Config/SysPref.pm and Koha/Util/SystemPreferences.pm

We only need the one from Koha::Config::SysPref and remove the whole
Koha::Util::SystemPreferences module.

Test plan:
 prove t/db_dependent/Circulation/issue.t
must return green

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>