Bug 11391: (follow-up) update DBIC schema classes

Bug 11391: (follow-up) update DBIC schema classes

This patch updates the DBIC schema class for Suggestion
to reflect the dropped default value for the suggesteddate
column.

To test:

[1] Create an empty Pg database and use the deployment script
    being worked in in bug 11390.  The deployment shoudl
    succeed without reporting any errors regarding the
    suggestions table.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>