qt: make the time tooltip a tooltip

This avoids to lose window focus when the mouse is over the seekbar (on
XFCE), and should also prevent the tooltip to appear resizeable on
Unity.

Probably fixes #20316

Signed-off-by: Hugo Beauzée-Luyssen <hugo@beauzee.fr>

modules/gui/qt/util/timetooltip.cpp

@@ -33,7 +33,7 @@
 TimeTooltip::TimeTooltip( QWidget *parent ) :
     QWidget( parent )
 {
-    setWindowFlags( Qt::Tool                    |
+    setWindowFlags( Qt::ToolTip                 |
                     Qt::WindowStaysOnTopHint    |
                     Qt::FramelessWindowHint     );