Bug 7904 - remove unnecessary path from SIP script

Bug 7904 - remove unnecessary path from SIP script

With the fixing of the namespace in the SIP code, we don't need to
modify the PERL5LIB to have the old one.

To test:
* do a package install using this and the other patches on bug 7904
* enable SIP
* make sure koha-start-sip and koha-stop-sip work

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>