Removed unused solar.h reference in filter

Change-Id: Ieffee3f06a12836b8a01dcebe2a6dc097b35dde9
Reviewed-on: https://gerrit.libreoffice.org/7520
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>