This commit updates the images used to illustrate Qt Widgets.
The commit also removes old unused images.
Task-number: QTBUG-69988
Change-Id: I89e363c6c854c36bb0d763532d4cb359bdc85a38
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
(cherry picked from commit 10e0ce7f8251fb4449152ba9979076930424d011)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>