fdo#63154 Removed unused solar.h reference in oox

Change-Id: I224bc31af9ecb77ad42357550e016b000ebf4837
Reviewed-on: https://gerrit.libreoffice.org/7519
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>