Bug 11061: remove unused routine Koha::Calendar::_mock_init

Bug 11061: remove unused routine Koha::Calendar::_mock_init

Bug 9209 removes the only occurrence to Koha::Calendar::_mock_init
The routine can be removed.

Test plan:
prove t/Calendar.t

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
I left that routine because I planned to do a follow-up for that so the
Calendar patch series was pushed soon. Nice catch Jonathan, works as expected.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Passes koha-qa.pl, t and xt

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit 55b13c092a6b4a1d1e89e08837e2f0c1d2bb84b9)
Signed-off-by: Fridolin SOMERS <fridolin.somers@biblibre.com>