[server/pyro] try to shutdown the repository properly
If RepositoryServer.trigger_events is not called we might miss a
QuitEvent and thus never shutdown the repository and its looping tasks.
[book] remove broken links to web.views.wdoc.ChangeLog{View,Action}
ChangeLogView and ChangeLogAction were removed in 3.16.0 (changeset
fa044b9157d7, https://www.cubicweb.org/2423532)
Closes #3369687