Remove wrong sentence in documentation
The removed line says to have the KAbstractFileItemActionPlugin as the parent of the returned actions. Contrarily, a few lines further down the documentation says to have the parentWidget as the parent of the returned actions.
The latter is the more recent addition to the documentation which was added because the former did not work out in some contexts.
The bug mentioned below contains a list of changes that made the parentWidget the parent of actions from KAbstractFileItemActionPlugins, which seems to have worked out because from what I can tell they were not reverted in the years since then.