Remove outdated note about autostart not working
Summary:
Just tested, worked fine. That line has been there since 5.0 days, I do
vaguely recall fixing this at some point.
CCBUG: 401399
Reviewers: Plasma
Subscribers: plasma-devel, kde-doc-english
Tags: Plasma, Documentation
Differential Revision: https://phabricator.kde.org/D17709