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

[Andrei Lebedev via cfe-commits]

andreil99 wrote:

Thanks, @cor3ntin!

I have installed the latest myst-parser (2.0.0) on the publishing bot. Will see how it will fly.

Please feel free to commit requirements.txt you have. I'll update it with the one with known-to-be-good versions frozen once we will confirm on that bot myst-parser 2.0.0.

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