fix pub date data type in reporter.classic_item_list

As noticed by Ben Shum in IRC, reporter.classic_item_list
had pub_date, a free text field, classified as "int". This
changes that to "text" to prevent errors.

Signed-off-by: Chris Sharp <csharp@georgialibraries.org>
Signed-off-by: Ben Shum <bshum@biblio.org>