Bug 22693: ILL "Price paid" column does not appear in column configuration

Bug 22693: ILL "Price paid" column does not appear in column configuration

Test Plan:
 - Navigate to ILL requests page from the main menu after setting up your ILL backend.
 - Observe that Price Paid column does not exist either here nor in the column configuration.
 - Apply patch
 - Observe that Price Paid column now appears in ILL requests table and in the column configuration page.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>