Auto merge of rust-lang#135059 - matthiaskrgr:rollup-0ka9o3h, r=matthiaskrgr

Rollup of 4 pull requests

Successful merges:

 - rust-lang#131729 (Make the `test` cfg a userspace check-cfg)
 - rust-lang#134241 (more concrete source url of std docs [V2])
 - rust-lang#135042 (taint fcx on selection errors during unsizing)
 - rust-lang#135049 (Remove unused fields from RepeatElementCopy obligation)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

std/src/lib.rs

@@ -89,7 +89,7 @@
 //! Check out the Rust contribution guidelines [here](
 //! https://rustc-dev-guide.rust-lang.org/contributing.html#writing-documentation).
 //! The source for this documentation can be found on
-//! [GitHub](https://github.com/rust-lang/rust).
+//! [GitHub](https://github.com/rust-lang/rust) in the 'library/std/' directory.
 //! To contribute changes, make sure you read the guidelines first, then submit
 //! pull-requests for your suggested changes.
 //!