Stop including changelog in PyPI description (#244)

It's linked prominently through project_urls already, it doesn't need to pollute the PyPI display of the README. Additionally it's sometimes necessary to push a change for a past release, but such changes cannot be added to that release's PyPI description as it's immutable.

setup.cfg

@@ -2,7 +2,7 @@
 name = flake8-comprehensions
 version = 3.2.2
 description = A flake8 plugin to help you write better list/set/dict comprehensions.
-long_description = file: README.rst, HISTORY.rst
+long_description = file: README.rst
 long_description_content_type = text/x-rst
 author = Adam Johnson
 author_email = me@adamj.eu