Rename "important traits" to something better

[Manishearth]

A lot of the feedback on https://internals.rust-lang.org/t/feedback-on-important-traits-rustdoc-feature/12752 had better suggestions for the "important traits" feature.

Some options were:

• Featured traits
• Key traits
• Notable traits

My personal preference is for "notable traits" because "important" is a much stronger value judgement whereas "notable" basically means "we thought you should know this" which is exactly what the feature does.

Thoughts? @rust-lang/rustdoc

We should pick something and rename.

[GuillaumeGomez]

I don't have strong feelings here but I think "Notable traits" is the best proposition out of the three.

[jyn514]

I agree 👍 , "featured traits" might be confused with cargo features and "key traits" has different connotations in my mind.

[camelid]

I'd be interested in doing this.

@rustbot claim