DolphinQt: Remove redundant window hints

Remove window hints clearing the flag Qt::WindowContextHelpButtonHint,
which is already off by default in Qt 6.

In Qt 5 this flag was set by default for QDialogs, and on Windows put a
? button in the corner of the title bar allowing users to activate Qt's
QWhatsThis help system for a given widget. Since we don't set that text
the ? button was useless and so we hid it manually.

Source/Core/DolphinQt/Config/Mapping/MappingWindow.cpp

@@ -65,7 +65,6 @@ MappingWindow::MappingWindow(QWidget* parent, Type type, int port_num)
     : QDialog(parent), m_port(port_num)
 {
   setWindowTitle(tr("Port %1").arg(port_num + 1));
-  setWindowFlags(windowFlags() & ~Qt::WindowContextHelpButtonHint);
 
   CreateDevicesLayout();
   CreateProfilesLayout();