Disable the "?" help button in all dialogs on Windows. Closes #7365.

src/app/main.cpp

@@ -212,6 +212,10 @@ int main(int argc, char *argv[])
         // 3. https://bugreports.qt.io/browse/QTBUG-46015
 
         qputenv("QT_BEARER_POLL_TIMEOUT", QByteArray::number(-1));
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 10, 0))
+        // this is the default in Qt6
+        app->setAttribute(Qt::AA_DisableWindowContextHelpButton);
+#endif
 #endif
 
 #if defined(Q_OS_MAC)