convert doc comment to regular comment

[euclio]

rust-lang/rust#57882 is modifying the unused_doc_comments lint to fire on mistakenly documented macro expansions. A crater run detected that this crate will break due to this change, likely because of the use of deny(unused_doc_comments) or deny(warnings).

While this kind of breakage is allowed under Rust's stability guarantees, I am opening PRs to affected crates to reduce the impact.

This PR protects your crate from future breakage by converting the offending doc comment to a regular comment.

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This change is