Globally disable WindowContextHelpButtonHint

Do set the global application flag AA_DisableWindowContextHelpButton
to avoid having to unset the default WindowContextHelpButtonHint
in every single dialog.

AA_DisableWindowContextHelpButton was added in Qt 5.10.

Change-Id: I21fe8bc5ddfa4c01ec7a799b04bfb6ff1c9d6d86
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/cmakeprojectmanager/cmakekitinformation.cpp

@@ -368,7 +368,6 @@ private:
 
         // Disable help button in titlebar on windows:
         Qt::WindowFlags flags = changeDialog->windowFlags();
-        flags &= ~Qt::WindowContextHelpButtonHint;
         flags |= Qt::MSWindowsFixedSizeDialogHint;
         changeDialog->setWindowFlags(flags);