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/Graphics/PostProcessingConfigWindow.cpp

@@ -42,7 +42,6 @@ PostProcessingConfigWindow::PostProcessingConfigWindow(EnhancementsWidget* paren
   }
 
   setWindowTitle(tr("Post-Processing Shader Configuration"));
-  setWindowFlags(windowFlags() & ~Qt::WindowContextHelpButtonHint);
 
   PopulateGroups();
   Create();