Bug 27415: Add note to ILLHiddenRequestStatuses

Bug 27415: Add note to ILLHiddenRequestStatuses

1. (Before adding patch) Go to 'Koha administration' - then to 'Global
system preferences'
2. On the left-hand side of the screen, go to 'Circulation' and then
'Interlibrary loans'
3. Look at the ILLHiddenRequestStatuses preferance - it should not have
any text talking about request codes in ILLSTATUS
4. Add the patch
5. Redo steps 1-3
6. The ILLHiddenRequestStatuses preferance should now have the sentance
'The request code can be found in the ILLSTATUS authorizes value
category.' under the value column.

Sponsored.by: Catalyst IT

JD Amended patch: fix commit title

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>