[llvm] [Atomic][doc] Fix outdated hook name and description (PR #66989)

[Alex Bradbury via llvm-commits]

https://github.com/asb approved this pull request.

Good catch, it looks like this was changed way back in f44fc5219f9e16f51de8eaa50a93fc6e7afcacba

https://github.com/llvm/llvm-project/pull/66989