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/CheatsManager.cpp

@@ -26,7 +26,6 @@ CheatsManager::CheatsManager(Core::System& system, QWidget* parent)
     : QDialog(parent), m_system(system)
 {
   setWindowTitle(tr("Cheats Manager"));
-  setWindowFlags(windowFlags() & ~Qt::WindowContextHelpButtonHint);
 
   connect(&Settings::Instance(), &Settings::EmulationStateChanged, this,
           &CheatsManager::OnStateChanged);