Device-specific font substitution is not used

This was only used for printer built in fonts, which was dropped in the
previous commit.

Change-Id: Iff62786284470ff3873c8d4b0aae0614bf69c7f3
Reviewed-on: https://gerrit.libreoffice.org/6859
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>