test: migrate diagnostics to snapbox

Author: heisen-li

tests/testsuite/diagnostics.rs

@@ -1,6 +1,5 @@
-#![allow(deprecated)]
-
 use cargo_test_support::project;
+use cargo_test_support::str;
 
 #[cargo_test]
 fn dont_panic_on_render() {
@@ -20,15 +19,14 @@ edition = "2021"
 
     p.cargo("check")
         .with_status(101)
-        .with_stderr(
-            "\
-error: invalid type: map, expected a sequence
+        .with_stderr_data(str![[r#"
+[ERROR] invalid type: map, expected a sequence
  --> Cargo.toml:6:3
   |
 6 | [[bench.foo]]
   |   ^^^^^
   |
-",
-        )
+
+"#]])
         .run();
 }