Move QApplication::autoSipEnabled() to public scope

The method is not meant be a slot.

warning: getter QApplication::autoSipEnabled possibly mismarked as a
slot [clazy-const-signal-or-slot]

[ChangeLog][QtWidgets][Potentially Source-Incompatible Changes]
bool QApplication::autoSipEnabled() is no longer a slot. Code such as
using QObject::connect() to connect to it as a slot or accessing it
through meta object system will have to be rewritten.

Pick-to: 6.5
Change-Id: I892a51120478f3c90e5834c8e3e00bc836b84c52
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/widgets/kernel/qapplication.h

@@ -129,12 +129,12 @@ Q_SIGNALS:
 
 public:
     QString styleSheet() const;
+    bool autoSipEnabled() const;
 public Q_SLOTS:
 #ifndef QT_NO_STYLE_STYLESHEET
     void setStyleSheet(const QString& sheet);
 #endif
     void setAutoSipEnabled(const bool enabled);
-    bool autoSipEnabled() const;
     static void closeAllWindows();
     static void aboutQt();