Fix typo in cargo-bench.md

[michaelkirk]

No description provided.

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @weihanglo (or someone else) some time within the next two weeks.

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[weihanglo]

Thanks for the contribution.

The build failed. See https://github.com/rust-lang/cargo/actions/runs/9046252088/job/24856873540?pr=13903#step:6:215:

Detected changes of man pages:
 M src/doc/src/commands/cargo-bench.md

Please run `cargo build-man` to rebuild the man pages
and commit the changes.

[weihanglo]

I'm going to close due to inactivity. Feel free to reopen if you have a chance to regenerate the man page.