Bug 28747: Clarify working on RestrictionBlockRenewal

Bug 28747: Clarify working on RestrictionBlockRenewal

To test, apply patch, restart services and reload page, confirm that now the syspref says "from the staff interface."

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit 8b8db671b4b1e7873ed34b3419b27342413c2b7e)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>