Change tests to support changes to suggestion

`rustc` will start marking the suggestions for prefacing unused bindings
with underscores as "maybe incorrect", which makes them no longer auto
applicable by `rustfix`.

Change done at rust-lang/rust#120470.

tests/testsuite/fix.rs

@@ -1502,6 +1502,7 @@ fn fix_shared_cross_workspace() {
     //     [FIXED] bar/src/../../foo/src/shared.rs (2 fixes)
     //     [FIXED] foo/src/shared.rs (2 fixes)
     p.cargo("fix --allow-no-vcs")
+        .env("__CARGO_FIX_YOLO", "1")
         .with_stderr_unordered(
             "\
 [CHECKING] foo v0.1.0 [..]

tests/testsuite/messages.rs

@@ -60,7 +60,7 @@ fn deduplicate_messages_basic() {
     let rustc_message = raw_rustc_output(&p, "src/lib.rs", &[]);
     let expected_output = format!(
         "{}\
-warning: `foo` (lib) generated 1 warning (run `cargo fix --lib -p foo` to apply 1 suggestion)
+warning: `foo` (lib) generated 1 warning[..]
 warning: `foo` (lib test) generated 1 warning (1 duplicate)
 [FINISHED] [..]
 [EXECUTABLE] unittests src/lib.rs (target/debug/deps/foo-[..][EXE])
@@ -103,7 +103,7 @@ fn deduplicate_messages_mismatched_warnings() {
     let expected_output = format!(
         "\
 {}\
-warning: `foo` (lib) generated 1 warning (run `cargo fix --lib -p foo` to apply 1 suggestion)
+warning: `foo` (lib) generated 1 warning[..]
 {}\
 warning: `foo` (lib test) generated 2 warnings (1 duplicate)
 [FINISHED] [..]