Rollup merge of rust-lang#106093 - notriddle:notriddle/docblock-short-overflow, r=GuillaumeGomez

rustdoc: remove no-op CSS from `.docblock-short`

The rules `overflow:hidden` and `text-overflow:ellipses` only have an effect if overflow occurs, which cannot happen because it will just line wrap instead.

These rules definitely became obsolete by rust-lang#77699, when the stylesheet was decidedly changed to have line wrapping in short docblocks, but given the bug it was fixing, this probably got broken earlier.

Author: matthiaskrgr