Flake: deadline exceeded in integration tests

https://pantheon.corp.google.com/cloud-build/builds;region=us-central1/9a17cdbe-a5cc-4739-a9d9-84bd32c8902d;step=1?project=rust-sdk-testing

```
Instance successfully deleted: Operation { client_operation_id: None, creation_timestamp: None, description: None, end_time: Some("2025-11-03T12:26:10.985-08:00"), error: None, http_error_message: None, http_error_status_code: None, id: Some(1792077791691583925), insert_time: Some("2025-11-03T12:23:54.990-08:00"), instances_bulk_insert_operation_metadata: None, kind: Some("compute#operation"), name: Some("operation-1762201434818-642b67e8b8946-41d0a18a-e5ff1a74"), operation_group_id: None, operation_type: Some("delete"), progress: Some(100), region: None, self_link: Some("https://www.googleapis.com/compute/v1/projects/rust-sdk-testing/zones/us-central1-a/operations/operation-1762201434818-642b67e8b8946-41d0a18a-e5ff1a74"), set_common_instance_metadata_operation_metadata: None, start_time: Some("2025-11-03T12:23:55.016-08:00"), status: Some(Done), status_message: None, target_id: Some(1449371987387658661), target_link: Some("https://www.googleapis.com/compute/v1/projects/rust-sdk-testing/zones/us-central1-a/instances/vm-j5fihr1tih2n18vq6v16ktt7o9jzo6bcoxov7of8zldwmxk42vzetx33y2hy"), user: Some("integration-test-runner@rust-sdk-testing.iam.gserviceaccount.com"), warnings: [], zone: Some("https://www.googleapis.com/compute/v1/projects/rust-sdk-testing/zones/us-central1-a") }
polling operation Operation { client_operation_id: None, creation_timestamp: None, description: None, end_time: None, error: None, http_error_message: None, http_error_status_code: None, id: Some(3881096463662755579), insert_time: Some("2025-11-03T12:27:00.098-08:00"), instances_bulk_insert_operation_metadata: None, kind: Some("compute#operation"), name: Some("operation-1762201619294-642b6898a67dc-293a5747-b2f09b96"), operation_group_id: None, operation_type: Some("insert"), progress: Some(0), region: None, self_link: Some("https://www.googleapis.com/compute/v1/projects/rust-sdk-testing/zones/us-central1-a/operations/operation-1762201619294-642b6898a67dc-293a5747-b2f09b96"), set_common_instance_metadata_operation_metadata: None, start_time: Some("2025-11-03T12:27:00.098-08:00"), status: Some(Running), status_message: None, target_id: Some(2319614829224308476), target_link: Some("https://www.googleapis.com/compute/v1/projects/rust-sdk-testing/zones/us-central1-a/instances/vm-pvq0o9wgxe4k3pjlkavh0b8ohzwpec1x13tg89mhzuaix0yt3ybesda9ulwh"), user: Some("integration-test-runner@rust-sdk-testing.iam.gserviceaccount.com"), warnings: [], zone: Some("https://www.googleapis.com/compute/v1/projects/rust-sdk-testing/zones/us-central1-a") }
Error: the request exceeded the request deadline error sending request for url (https://compute.googleapis.com//compute/v1/projects/rust-sdk-testing/zones/us-central1-a/operations/operation-1762201619294-642b6898a67dc-293a5747-b2f09b96/wait?%24alt=json)
Caused by:
0: error sending request for url (https://compute.googleapis.com//compute/v1/projects/rust-sdk-testing/zones/us-central1-a/operations/operation-1762201619294-642b6898a67dc-293a5747-b2f09b96/wait?%24alt=json)
1: operation timed out
failures:
tests::instance_samples
```

I think we timed out polling for an instance to be created. Somewhere in here:

https://github.com/googleapis/google-cloud-rust/blob/b0dcf168dea463b802f4fe109053629a0e0d950f/guide/samples/src/compute/compute_instances_operation_check.rs#L22