Update tests for new TRPL chapter order

tests/ui/pattern/usefulness/refutable-pattern-errors.stderr

@@ -13,7 +13,7 @@ LL |     let (1, (Some(1), 2..=3)) = (1, (None, 2));
    |         ^^^^^^^^^^^^^^^^^^^^^ patterns `(i32::MIN..=0_i32, _)` and `(2_i32..=i32::MAX, _)` not covered
    |
    = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
-   = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
+   = note: for more information, visit https://doc.rust-lang.org/book/ch19-02-refutability.html
    = note: the matched value is of type `(i32, (Option<i32>, i32))`
 help: you might want to use `if let` to ignore the variants that aren't matched
    |