Fix mailmap duplicates, Carol and Brian.

[russmack]

This fix corrects the .mailmap file so that Carol (Nichols || Goulding) appears only once, and Brian Anderson also appears only once.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @nikomatsakis (or someone else) soon.

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[Mark-Simulacrum]

r? @steveklabnik -- I think you've worked the most with this file.

[steveklabnik]

@bors: r+ rollup

thanks!

[bors]

📌 Commit 9a56286 has been approved by steveklabnik