Remove 'legacy' action for wpsc_meta_boxes

Looking through the code in wpsc-admin/admin.php I see we have a call to `add_action( 'admin_footer', 'wpsc_meta_boxes' );`. The custom meta boxes are already being set via a callback in wpsc-core/wpsc-functions.php.

Is this call around for some legacy reason that is no longer needed?

Metaboxes should really be called on the callback (as it is) or on add_meta_boxes.