[libcxx-commits] [libcxx] [libc++][doc] Update the release notes for LLVM 19. (PR #99061)

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llvmbot wrote:

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Failed to cherry-pick: [e9bb4e3](https://github.com/llvm/llvm-project/commit/e9bb4e303b949f955042158567eb83000a6e7634)

https://github.com/llvm/llvm-project/actions/runs/10063126078

Please manually backport the fix and push it to your github fork.  Once this is done, please create a [pull request](https://github.com/llvm/llvm-project/compare)

https://github.com/llvm/llvm-project/pull/99061