Bump required version of KF5 to 5.69.0

Summary: KCrash::setErrorMessage() was introduced in 5.69.0.

Reviewers: #frameworks, dfaure, apol, sitter

Reviewed By: sitter

Subscribers: kde-frameworks-devel, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D28095