Fix doc link to Eq trait from PartialEq trait
Fix doc link to Eq trait from PartialEq trait

The `Eq` link was incorrectly going to the `eq` method of `PartialEq`
instead of to the `Eq` trait.

aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust