Use automatic intra-doc links

[mgeisler]

When rust-lang/rust#74430 lands in a stable Rust release, we should go through the doc strings and change them from

/// Use the [`wrap`] function...
/// [`wrap`]: fn.wrap.html

to

/// Use the [`wrap`] function...

That is, we can rely on rustdoc to automatically find the right target for internal documentation links.