Stop advertising titlebar "What's This?" help button
The "What's This?" feature has been transformed into an expandable tooltip for KDE apps in frameworks/kxmlgui!45 (merged) (merged).
Now the text is shown by pressing the Shift key while one of these expandable tooltips is visible. As a result, there is no longer a need for a second redundant method of invoking the feature, so let's hide the button to do so from dialog windows by setting Qt::AA_DisableWindowContextHelpButton to true.