[libcxx] [llvm] [docs] Fix malformed csv files (PR #80567)

[Louis Dionne via llvm-commits]

ldionne wrote:

@wusatosi What dependencies do you need to implement this check? If there are basically no dependencies that need to be installed, I would add it so that it gets checked as part of `check-cxx`, I think. But otherwise I would probably add it to `.github/workflows/libcxx-check-generated-files.yml` (and rename that file to something like `libcxx-lightweight-checks.yml`.

https://github.com/llvm/llvm-project/pull/80567