Adjusted CppunitTest_sw_ooxmlexport for Mac Retina 13"

Change-Id: I208064aef57e0ef4b149183869f0908580e189f1
Reviewed-on: https://gerrit.libreoffice.org/13528
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>