Use assert_matches (#4756)

assert_matches is soon to be in std but is experimental for now.

codex-rs/utils/readiness/src/lib.rs

@@ -176,6 +176,7 @@ mod tests {
     use super::ReadinessFlag;
     use super::Token;
     use super::errors::ReadinessError;
+    use assert_matches::assert_matches;
 
     #[tokio::test]
     async fn subscribe_and_mark_ready_roundtrip() -> Result<(), ReadinessError> {
@@ -244,6 +245,6 @@ mod tests {
             .subscribe()
             .await
             .expect_err("contended subscribe should report a lock failure");
-        assert!(matches!(err, ReadinessError::TokenLockFailed));
+        assert_matches!(err, ReadinessError::TokenLockFailed);
     }
 }