Sync metadata

www.agileplannerapp.com/boards/173808/cards/5444

Publisher has an "Edit in Panopticon" link which
allows section, slug and department to be edited
for an edition. Once artefact was edited in
Panopticon these changes were not be synced
back to the Edition.

commit https://github.com/alphagov/govuk_content_models/commit/99d3e5152d7ec9fdb3c9c912d6bd0d8a458defe2 is to make the build green by using
a compatible govspeak version. see https://github.com/alphagov/govspeak/pull/34
This doesn't look quite correct, as this will also allow govspeak 3.x.  Maybe this should be `~> 2.0.2`.