In qtwindowlistmenu.cpp - setting the shortcut "Ctrl+F4" on the close action makes it unavailable

In QtWindowListMenu::QtWindowListMenu(QWidget *parent) we have the following code:
...
QAction *act = new QAction(tr("Cl&ose"), stdGroup);
act->setShortcut(tr("Ctrl+F4"));
act->setStatusTip(tr("Close the active window"));
...

The problem is that the shortcut Ctrl+F4 is already implemented with the mdiArea. So by setting the act->setShortcut(tr("Ctrl+F4")), this shortcut is redundant and becomes ambiguous.

When using the shortcut, it does not work and the user gets the warning:
QAction::eventFilter: Ambiguous shortcut overload: Ctrl+F4

This line needs to be removed. The updated file and git patch candidate are included.