Reduce clippy lints page size

[GuillaumeGomez]

Follow-up of #15208.

Removed some unneeded wrappings and shortened some CSS class name.

The diff is big because of one indent level getting removed. :-/

Before this PR: 1751301
With this PR: 1663634
Reduction: -5%

r? @samueltardieu

changelog: Reduce page size and number of DOM elements on clippy lints page

[samueltardieu]

I got this in the console once

Uncaught TypeError: can't access property "innerText", elem.querySelector(...) is null
    allLints http://localhost:8000/script.js:253
    getAllLints http://localhost:8000/script.js:245
    filterLints http://localhost:8000/script.js:323
    <anonymous> http://localhost:8000/script.js:611
[script.js:253:33](http://localhost:8000/script.js)
    allLints http://localhost:8000/script.js:253
    map self-hosted:175
    getAllLints http://localhost:8000/script.js:245
    filterLints http://localhost:8000/script.js:323

but can't reproduce it. I'll assume this was a transient problem on my side.

[GuillaumeGomez]

Maybe it loaded the old script initially? Strange. Thanks for taking a look!