[TerminalDisplay] Change the mouse cursor shape back to beam on leaveEvent

Test case:

• press Ctrl and hover on a link, the mouse cursor changes to a hand, click the link and a browser or text editor ... etc is launched
• if you have focus stealing prevention set to low or none, the launched app could cover the terminal window and the mouse cursor will be stuck at the hand shape, even when the mouse cursor enters the konsole window again, until you hover on a link again