Fix doc builds for bool kwargs (#44686)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/43669
The bool will still link to https://docs.python.org/3/library/functions.html#bool.
Tested using bmm:
![image](https://user-images.githubusercontent.com/16063114/93156438-2ad11080-f6d6-11ea-9b81-96e02ee68d90.png)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/44686
Reviewed By: ngimel
Differential Revision: D23703823
Pulled By: mruberry
fbshipit-source-id: 7286afad084f5ab24a1254ad84e5d01907781c85