Bug 18169: Make 'before' param non mandatory for Koha::Patrons->anonymise_issue_history

Bug 18169: Make 'before' param non mandatory for Koha::Patrons->anonymise_issue_history

From opac-privacy.pl:

    # delete all reading records for items returned
    # uses a hardcoded date ridiculously far in the future

    my $rows = eval {
        Koha::Patrons->search({ 'me.borrowernumber' => $borrowernumber })->anonymise_issue_history( { before => '2999-12-12' } );
    };

It sounds better to make this before parameter not mandatory, and remove the condition from the sql query if it is not passed.

Test plan:
1. Anonymise your reading history at the OPAC.
2. Confirm that all your reading history has been anonymised

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>