`hir::Body`'s documentation incorrectly suggests it doesn't contain parmaeter info for closures

### Location

https://doc.rust-lang.org/nightly/nightly-rustc/rustc_hir/hir/struct.Body.html

### Summary

Noticed this in rust-lang/rust-clippy#12981. The documentation says "a function" which I assume was meant to imply both a function/method call and closure while explicitly excluding constant values, yet closures weren't explicitly included which can lead to confusion.