Make enable_gui a staticmethod again

IPython/frontend/terminal/interactiveshell.py

@@ -358,6 +358,7 b' class TerminalInteractiveShell(InteractiveShell):'
     using_paste_magics = CBool(False)
 
     # In the terminal, GUI control is done via PyOS_InputHook
+    @staticmethod
     def enable_gui(gui=None, app=None):
         """Switch amongst GUI input hooks by name.
         """