Bug 17824: Remove C4::Members::GetBorrowersWhoHaveNeverBorrowed

Bug 17824: Remove C4::Members::GetBorrowersWhoHaveNeverBorrowed

This subroutine is no longer in used and can be removed.

Test plan:
  git grep GetBorrowersWhoHaveNeverBorrowed
must not return any results

NOTE: grep -i getborrowerswhohave `find . -type f`
      works well enough to find the cleanborrowers.pl too.

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>