VS2013: Adjust python3 to 12.0 vcproj version

Change-Id: Ic4566e8a199d3f31d6d4cb2d3fd41ad7b762c02a
Reviewed-on: https://gerrit.libreoffice.org/10162
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>