ci: fix new error output from rustc 1.63.0 (#4905)

tests-build/tests/fail/macros_core_no_default.stderr

@@ -1,5 +1,5 @@
 error: The default runtime flavor is `multi_thread`, but the `rt-multi-thread` feature is disabled.
- --> tests/fail/macros_core_no_default.rs:3:1
+ --> $DIR/macros_core_no_default.rs:3:1
   |
 3 | #[tokio::main]
   | ^^^^^^^^^^^^^^

tests-build/tests/fail/macros_dead_code.stderr

@@ -1,4 +1,4 @@
-error: function is never used: `f`
+error: function `f` is never used
  --> $DIR/macros_dead_code.rs:6:10
   |
 6 | async fn f() {}