Qt: fix padding on the speed selector

Close #13329

(cherry picked from commit 93ff2c22cc8861e589f8034e3af4db2527c07550)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/gui/qt4/components/interface_widgets.cpp

@@ -483,6 +483,7 @@ SpeedLabel::SpeedLabel( intf_thread_t *_p_intf, QWidget *parent )
     DCONNECT( THEMIM, inputChanged( ),
               speedControl, activateOnState() );
 
+    setContentsMargins(4, 0, 4, 0);
     setRate( var_InheritFloat( THEPL, "rate" ) );
 }