Do not set Qt::ToolTip flag for QShapedPixmapWindow

This hint is not really needed in the first place and only causes
problems in some environments.

For example in KDE, the compositor animates changes in position and size
for all ToolTip windows. However, this is not wanted here because we use
this window as a thumbnail for a drag-and-drop operation.
Before this patch the dragged element would lag significantly behind the
cursor. Now it works as expected, i.e. the dragged element follows the
cursor immediately.

Fixes: QTBUG-98048
Change-Id: I49ef453c05228ce1a9336a9463046a794650acae
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Liang Qi <liang.qi@qt.io>

src/gui/kernel/qshapedpixmapdndwindow.cpp

@@ -20,7 +20,7 @@ QShapedPixmapWindow::QShapedPixmapWindow(QScreen *screen)
     QSurfaceFormat format;
     format.setAlphaBufferSize(8);
     setFormat(format);
-    setFlags(Qt::ToolTip | Qt::FramelessWindowHint | Qt::X11BypassWindowManagerHint
+    setFlags(Qt::FramelessWindowHint | Qt::BypassWindowManagerHint
              | Qt::WindowTransparentForInput | Qt::WindowDoesNotAcceptFocus);
 }