Deprecate KRecursiveFilterProxyModel
Summary: It is not needed since Qt 5.10
Reviewers: kossebau, dfaure, davidedmundson
Reviewed By: dfaure, davidedmundson
Subscribers: kde-frameworks-devel
Tags: Frameworks, KF6
Maniphest Tasks: T12269
Differential Revision: https://phabricator.kde.org/D25546