Rollup merge of #140248 - GuillaumeGomez:fix-impl-block-items-indent, r=notriddle

Fix impl block items indent

Fixes #139771.

Now, all impl block "before impl block items" indent are the same (ie, item info and documentation).

With this fix, it looks like this:

![Screenshot From 2025-04-24 12-32-40](https://github.com/user-attachments/assets/907803a2-2949-4d01-afa5-fc3132d10ff2)

You can test it [here](https://rustdoc.crud.net/imperio/fix-impl-block-items-indent/foo/struct.Context.html).

r? `@notriddle`