remove use of the term "blacklist" from docs/cpp/source/Doxyfile (#41450)
Summary:
As requested in https://github.com/pytorch/pytorch/issues/41443
Pull Request resolved: https://github.com/pytorch/pytorch/pull/41450
Reviewed By: ezyang
Differential Revision: D22561782
Pulled By: SplitInfinity
fbshipit-source-id: b38ab5e2725735d1f0c70a4d0012678636e992c3
