The merge took place here https://phabricator.kde.org/D1029545c37a64e1cc lost some docbook changes from 7034b50c5c9e, let's restore
them.
Also bump date and releaseinfo, and remove entities which now come from
`kdoctools`.
Thanks to @gregormi for the initial version of the patch, and @lueck for
help with the docbook.
Depends on D10529