Rollup merge of #145712 - notJoon:fix/outdate-link, r=lqd

Update outdated link in bound region comments

While reading the implementation code for bound regions, I found that a link in the comments was outdated. I've updated it with a link to the corresponding documentation in the rustc dev guide that covers the same content.

prev link: https://rustc-dev-guide.rust-lang.org/early-late-bound-params/early-late-bound-summary.html (404 error)
updated: https://rustc-dev-guide.rust-lang.org/early_late_parameters.html