A few examples seem to have copied and pasted a help action "About
&Qt" that triggered QCoreApplication::quit. This does not look like
best practice. Use QApplication::aboutQt instead.
Pick-to: 6.6 6.5
Task-number: QTBUG-111228
Change-Id: I1887a3c999d752a24c7c4d3cabc4a5d63b29b966
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>