pytype: stop excluding changegroup.py
The false positives that were detected seem to be related to what happens to the
variables after the local methods are used:
File "/mnt/c/Users/Matt/hg/mercurial/changegroup.py", line 353, in ondupchangelog:
No attribute 'append' on range [attribute-error]
In Union[List[nothing], range]
File "/mnt/c/Users/Matt/hg/mercurial/changegroup.py", line 357, in onchangelog:
No attribute 'update' on None [attribute-error]
Differential Revision: https://phab.mercurial-scm.org/D11912