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/RiivolutionBootWidget.cpp

@@ -46,7 +46,6 @@ RiivolutionBootWidget::RiivolutionBootWidget(std::string game_id, std::optional<
       m_base_game_path(std::move(base_game_path))
 {
   setWindowTitle(tr("Start with Riivolution Patches"));
-  setWindowFlags(windowFlags() & ~Qt::WindowContextHelpButtonHint);
 
   CreateWidgets();
   ConnectWidgets();