[clang] [Documentation] Replace recommonmark by myst-parser (PR #65664)

[Tobias Hieta via cfe-commits]

tru wrote:

Seems like a nice cleanup on top of the fact that we don't have to use a deprecated module. I am guessing it didn't cause any output errors.

Regarding build-bots, I am unsure where we automatically build the documentation. Pushing the docs to the main branch will rebuild and put them on llvm.org, But not sure where that happens. Maybe we should have a `requirements.txt` for documentation building and add that somewhere in the tree and have our bots always install that instead of each bot having its own list of python modules.

cc @tstellar 


https://github.com/llvm/llvm-project/pull/65664