[clang-tools-extra] [clang-doc] modify basic-project test (PR #97684)

[Paul Kirth via cfe-commits]

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

LGTM, but let’s update the pr title and description to match the current patch. 

Also, a title like modify tests isn’t very informative. Something like “Support markdown and simplify checks” seems more appropriate. Additionally, those two aspects seem like they could be separate PRs, though I won’t require that. 

https://github.com/llvm/llvm-project/pull/97684