fdo#75757: remove inheritance to std::vector

... by boost::ptr_vector.
Originally TextCharAttribList::Clear() was never called with false,
so this drops the argument.

Change-Id: I0306cd787dd38de0960af38afe9c08a910195b26
Reviewed-on: https://gerrit.libreoffice.org/10549
Tested-by: LibreOffice gerrit bot <gerrit@libreoffice.org>
Reviewed-by: David Tardon <dtardon@redhat.com>
Tested-by: David Tardon <dtardon@redhat.com>