Do not warn in rustdoc test.

src/test/rustdoc-ui/display-output.rs

@@ -10,6 +10,6 @@
 /// #![warn(unused)]
 /// let x = 12;
 ///
-/// fn foo(x: &std::fmt::Display) {}
+/// fn foo(x: &dyn std::fmt::Display) {}
 /// ```
 pub fn foo() {}

src/test/rustdoc-ui/display-output.stdout

@@ -5,16 +5,6 @@ test $DIR/display-output.rs - foo (line 9) ... ok
 successes:
 
 ---- $DIR/display-output.rs - foo (line 9) stdout ----
-warning: trait objects without an explicit `dyn` are deprecated
-  --> $DIR/display-output.rs:13:12
-   |
-LL | fn foo(x: &std::fmt::Display) {}
-   |            ^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn std::fmt::Display`
-   |
-   = note: `#[warn(bare_trait_objects)]` on by default
-   = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
-   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
-
 warning: unused variable: `x`
   --> $DIR/display-output.rs:11:5
    |
@@ -31,13 +21,13 @@ LL | #![warn(unused)]
 warning: unused variable: `x`
   --> $DIR/display-output.rs:13:8
    |
-LL | fn foo(x: &std::fmt::Display) {}
+LL | fn foo(x: &dyn std::fmt::Display) {}
    |        ^ help: if this is intentional, prefix it with an underscore: `_x`
 
 warning: function is never used: `foo`
   --> $DIR/display-output.rs:13:4
    |
-LL | fn foo(x: &std::fmt::Display) {}
+LL | fn foo(x: &dyn std::fmt::Display) {}
    |    ^^^
    |
 note: the lint level is defined here
@@ -47,7 +37,7 @@ LL | #![warn(unused)]
    |         ^^^^^^
    = note: `#[warn(dead_code)]` implied by `#[warn(unused)]`
 
-warning: 4 warnings emitted
+warning: 3 warnings emitted