fdo#75757: remove inheritance to std::vector

typedefs just work.

Change-Id: Ib91c0d4c383b5efac1ad9b93e574dec62e8234a4
Reviewed-on: https://gerrit.libreoffice.org/10754
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>