Bug 11123: remove two unused routines from C4::Accounts

C4::Accounts::fixcredit and C4::Accounts::refund are marked as
deprecated and are not used. They can be removed.

Use:
  git grep fixcredit
  git grep refund
and verify these routines are not currently in used.

Bonus: The module exports reconcileaccount which is not defined. The
export is removed too.

MLT: Ran qa tool on this patch with no issues either.

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>