Rollup merge of #148713 - InvalidPathException:master, r=lcnr

rustc_borrowck: fix async closure error note to report AsyncFn rather than Fn

Fixes rust-lang/rust#148391

Root cause:
`async` closures are treated like plain `Fn` closures because we never updated their kind after adding the async coroutine path.

Symptom:
The compiler note tells users `closure implements Fn…`, which is wrong for async closures and made the error message confusing. Notably `FnMut` does not suffer from this issue.

Fix:
Fixed the wording

Testing:
Updated a UI test stderr file to reflect the correct wording. It also clearly demonstrates what was wrong.

Author: JonathanBrouwer