vcl/source/outdev/outdev.cxx: drop unused svsys.h header

Change-Id: I21308351e86372ce938480a8514415756f9bf549
Reviewed-on: https://gerrit.libreoffice.org/10165
Tested-by: LibreOffice gerrit bot <gerrit@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>