Revert "Qt: force main window maximum size to be some big enough"

This reverts commit b5a43deb.

This is not enough and introduces more regressions

modules/gui/qt4/main_interface.cpp

@@ -260,7 +260,6 @@ MainInterface::MainInterface( intf_thread_t *_p_intf ) : QVLCMW( _p_intf )
     if( b_minimalView )
         toggleMinimalView( true );
 
-    setMaximumSize( QSize( 16386, 16386 ) );
     computeMinimumSize();
 }