Bug 21207: Remove unused RM C4::Overdues::GetItems sub

Bug 21207: Remove unused RM C4::Overdues::GetItems sub

Test plan:
  git grep GetItems
  | grep -v GetItemsInCollection
  | grep -v GetItemsForInventory
  | grep -v GetItemsInfo
  | grep -v GetItemsLocationInfo
  | grep -v GetItemsAvailable
  | grep -v GetItemsByBiblioitemnumber

should not return any occurrences of code in perl scripts

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>