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.

Thanks for digging up the history.  I would have approved without, but feel better with.  Using the colorizer close method to close a window seemed flakey to me, and it seems someone else thought the same long ago.  I suspect the machinery was left to avoid breaking external uses.  PEP 434 changed this avoidance being *necessary*.  (I am sure I have seen a SO answer with percolator + colorizer, as in turtledemo.)

IDLE has had a too many shutdown bugs and still has some.  Not adding one was my main concern when reviewing.

New changeset b9f0354efce95b7557bc43ea193c4b652cd28392 by Cheryl Sabella in branch 'master':
bpo-36152: IDLE: Remove unused parameter from colorizer (GH-12109)
https://github.com/python/cpython/commit/b9f0354efce95b7557bc43ea193c4b652cd28392

New changeset 70852b1eb6fbcc41fe9cad042e9ca61c5148fbda by Miss Islington (bot) in branch '3.7':
bpo-36152: IDLE: Remove unused parameter from colorizer (GH-12109)
https://github.com/python/cpython/commit/70852b1eb6fbcc41fe9cad042e9ca61c5148fbda