Revert "Bring QWindowPrivate::deliverUpdateRequest() back temporarily"

This reverts commit 6ada4155af.

The fix to use new private API landed in qtwayland e3fa740d20.

Task-number: QTBUG-67480
Change-Id: Ie01e4b423ca326b81740f195562244e733a66d72
Reviewed-by: Johan Helsing <johan.helsing@qt.io>

src/gui/kernel/qwindow.cpp

@@ -2358,12 +2358,6 @@ bool QWindow::event(QEvent *ev)
     return true;
 }
 
-void QWindowPrivate::deliverUpdateRequest()
-{
-    if (platformWindow)
-        platformWindow->deliverUpdateRequest();
-}
-
 /*!
     Schedules a QEvent::UpdateRequest event to be delivered to this window.
 

src/gui/kernel/qwindow_p.h

@@ -124,8 +124,6 @@ public:
     bool applyCursor();
 #endif
 
-    void deliverUpdateRequest();
-
     QPoint globalPosition() const;
 
     QWindow *topLevelWindow() const;