Remove as deprecated marked classes and functions

Summary:
The in Qt 5.13 as deprecated respectively obsolete marked classes,
methods and functions were substituted by its, in the compiler
message or documentation suggested, alternatives.

Test Plan: Compiler runs without warnings

Reviewers: #kde_edu, apol

Reviewed By: apol

Subscribers: apol, kde-edu

Tags: #kde_edu

Differential Revision: https://phabricator.kde.org/D22497