fix: fix clippy issue caught by cargo but not bazel (#16345)

I noticed that
https://github.com/openai/codex/actions/workflows/rust-ci-full.yml
started failing on my own PR,
https://github.com/openai/codex/pull/16288, even though CI was green
when I merged it.

Apparently, it introduced a lint violation that was [correctly!] caught
by our Cargo-based clippy runner, but not our Bazel-based one.

My next step is to figure out the reason for the delta between the two
setups, but I wanted to get us green again quickly, first.

codex-rs/core/tests/suite/client.rs

@@ -804,6 +804,7 @@ async fn provider_auth_command_refreshes_after_401() {
 ///
 /// The caller owns the server-side assertions, so this helper only validates that the request
 /// reaches `Completed` without surfacing an auth or transport error to the client.
+#[expect(clippy::expect_used, clippy::unwrap_used)]
 async fn send_provider_auth_request(server: &MockServer, auth: ModelProviderAuthInfo) {
     let provider = ModelProviderInfo {
         name: "corp".into(),