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

[Michał Górny via cfe-commits]

mgorny wrote:

I'm sorry for being late to the party but what's the rationale for removing support for building manpages without myst-parser, that FWICS isn't used for manpages at all? I don't see any answer neither in the commit message, nor in this thread. It really feels like you've just *shrugged* and removed it without any consideration for the prior effort to make things work better.

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