rustdoc: change color of trait types

[liigo]

Fixes #24441

Preview:

[rust-highfive]

r? @alexcrichton

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[alexcrichton]

r? @steveklabnik

(not much of a UI guy)

[ftxqxd]

I personally much prefer the old colour. I’d say that #24441 is really more of a bug in Chrome than anything else—Chrome really shouldn’t expect every website to avoid using a text colour that is close to the orange it uses to highlight search results.

[steveklabnik]

I am not a UX person either, so I don't know. I do know that I didn't like the old color much. Let's see how we feel about this, it's always easy to fix to another color if it looks too weird.

[steveklabnik]

@bors: r+ rollup

[bors]

📌 Commit 31c3e7e has been approved by steveklabnik

[gkoz]

I personally much prefer the old colour. I’d say that #24441 is really more of a bug in Chrome than anything else

Ditto. This feels like a regression.