message: docs: update link for raw string literal docs
diff: @@ -56,7 +56,7 @@ it to match anywhere in the text. Anchors can be used to ensure that the
  full text matches an expression.
  This example also demonstrates the utility of
  -[raw strings](https://doc.rust-lang.org/stable/reference.html#raw-string-literals)
  +[raw strings](https://doc.rust-lang.org/stable/reference/tokens.html#raw-string-literals)
  in Rust, which
  are just like regular strings except they are prefixed with an `r` and do
  not process any escape sequences. For example, `"\\d"` is the same
  