Pinned issue's border is very bold/bright in dark mode #4867

Description

The pinned issues on top of the page is very bright. I think making it look like other borders in the page would be great and easy for the user.

Right Now	How it Should Be

Although 3806 PR says it works on this issue, it still is very bright right now. Please update me if I am missing something.

Thanks.

Screenshot

No response

Example URL

https://github.com/sindresorhus/refined-github/issues