Bug 29405: Fix date_renewed attribute format in patron spec

Bug 29405: Fix date_renewed attribute format in patron spec

This patch just adds the 'date' format string to ensure we are
validating the input/output of the date_renewed field correctly.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit e165f57f248fbb5166834d5117caef4fddf3c3e3)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>