Fix Typo in Barrier::wait documentation

[CryZe]

This should be have instead of has.

[rust-highfive]

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

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[GuillaumeGomez]

Thanks!

r=me @steveklabnik @Manishearth

[Manishearth]

@bors r=GuillaumeGomez

[bors]

📌 Commit 32edf1d has been approved by GuillaumeGomez

[GuillaumeGomez]

@bors rollup

[Manishearth]

@bors rollup

[GuillaumeGomez]

This seems not efficient.

[Manishearth]

rollup should work for you if you have try access -- I don't know if you do