fix format

Author: fangchenli

setup.cfg

@@ -99,8 +99,6 @@ ignore =
     E711,  # comparison to none should be 'if cond is none:'
 exclude =
     doc/source/development/contributing_docstring.rst,
-    # work around issue of undefined variable warnings
-    # https://github.com/pandas-dev/pandas/pull/38837#issuecomment-752884156
     doc/source/getting_started/comparison/includes/*.rst
 
 [tool:pytest]