Rollup merge of #105539 - GuillaumeGomez:hashtag-prepended-lines-non-rust, r=notriddle

Rollup merge of #105539 - GuillaumeGomez:hashtag-prepended-lines-non-rust, r=notriddle

rustdoc: Only hide lines starting with `#` in rust code blocks

Fixes https://github.com/rust-lang/rust/issues/105527.

So before approving, this is a big question: in rust code blocks, in a line starts with a `#`, we hide it in the output. However, should we do the same for non-rust code blocks too? I think it's a bit problematic to do it because `#` can be used for many things but I prefer to check first with everyone (might also be worth updating documentation too).

cc ``@rust-lang/rustdoc``
r? ``@notriddle``