fdo#75757: remove inheritance to std::vector

... for PaneStyleContainer and ViewStyleContainer.

Change-Id: I6a6e2b1733266f54a94a49ab491cf854eb5df492
Reviewed-on: https://gerrit.libreoffice.org/10847
Reviewed-by: David Tardon <dtardon@redhat.com>
Tested-by: David Tardon <dtardon@redhat.com>