Bug 20698: Remove obsolete template: transfer-slip.tt

Bug 20698: Remove obsolete template: transfer-slip.tt

This patch removes an unused template file, circ/transfer-slip.tt. Its
use was removed by Bug 7001:

http://git.koha-community.org/gitweb/?p=koha.git;a=commitdiff;h=a9ded4fa008668df8c485fbbc76efa3cc9cc00d7#patch12

To test, apply the patch and confirm that the file has been removed.
Confirm that no references to the template exist in the codebase.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>