bug 5563 change note about cover images on enhanced content

bug 5563 change note about cover images on enhanced content

on the enhanced content tab of system
preferences it says that Koha will pick
the first cover image - but in fact it
shows them all - that note needs to be
updated to properly warn of the expected
behavior.

Signed-off-by: Ian Walls <ian.walls@bywatersolutions.com>
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
(cherry picked from commit 606f9784199722bd661d60be1944aa97c6a8971c)

Signed-off-by: Chris Nighswonger <chris.nighswonger@gmail.com>