[clang] [clang-tools-extra] Fix cross-references in Clang attribute reference (PR #142967)

[Aaron Ballman via cfe-commits]

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

LGTM! This all looks correct to me, so LG assume precommit CI doesn't find issues with the Sphinx markdown.

https://github.com/llvm/llvm-project/pull/142967