Remove the unused `close_when_done` parameter from `close()` in `colorizer.ColorDelegator()`.

* The second parameter to close() is called `close_when_done` and it is expected to contain a toplevel widget that has a destroy() method.

* Originally, the editor window had code that would send self.top (if colorizing was in process) as the value for this parameter:

            doh = colorizing and self.top
            self.color.close(doh) # Cancel colorization

* This was changed via this commit (https://github.com/python/cpython/commit/8ce8a784bd672ba42975dec752848392ff9a7797) in 2007 to instead be:
 
            self.color.close(False)
            self.color = None

The value of `False` made it so the destroy code in colorizer wouldn't be run even though `None` or leaving the parameter off would have been more clear.

In any case, this `close_when_done` hasn't been used since 2007.