Bug 21650: Remove the subroutine C4::Items::GetLastAcquisitions

Bug 21650: Remove the subroutine C4::Items::GetLastAcquisitions

C4::Items::GetLastAcquisitions has been added by
  commit 7753bbad4fb4df47c8fb4f959fc68764a71cb623
  Adding Some new functions

(?)

Apparently it has never been used, we should remove it to avoid unnecessary maintenance.

Test plan:
  git grep GetLastAcquisitions
must not return any results

NOTE: POD Coverage test failure is expected on removal

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>