Bug 12752: FIX letter names in 3.15.00.041

Bug 12752: FIX letter names in 3.15.00.041

3.15.00.041 was wrong, the name of the letter should not always been the
name of the first HOLD notice.
PREDUE_PHONE should be updated with the first name of the PREDUE notice,
same for OVERDUE_PHONE and OVERDUE

Signed-off-by: Chris Cormack <chrisc@catalyst.net.z>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>

Signed-off-by: Brendan Gallagher <brendan@bywatersolutions.com>
(cherry picked from commit 6d52cd63f351cd56f36492b80c10c0d8568ef03d)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>