Bug 21441: Fix wrong reference to a 'holds' table on system information tab

Bug 21441: Fix wrong reference to a 'holds' table on system information tab

It looks like a typo snuck in on the about page, listing a holds
table instead of reserves.

To test:
- Manually create the same PK (reserve_id) in reserves and old_reserves
- Verify that the message on about > system information now
  correctly lists those tables (not holds and old_reserves)

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>