Fix incorrect link in Option documentation.

[ghost]

No description provided.

[rust-highfive]

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

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[steveklabnik]

@bors: r+ rollup

[bors]

📌 Commit 86de427 has been approved by steveklabnik

[steveklabnik]

Thanks so much!

[killercup]

You should probably move the link to a new paragraph as it is also visible http://doc.rust-lang.org/std/option/#enums.

cc @steveklabnik