GA tests running into 'has hit the rate limit with Maven Central' at mvn install

A few of the native image tests have been running into the following error at the mvn install stage:

```
HTTP request sent, awaiting response... 429 Your IP: 68.154.117.33 has hit the rate limit with Maven Central. Too many requests. Find out more in https://www.sonatype.com/blog/maven-central-and-the-tragedy-of-the-commons
2025-07-17 01:52:24 ERROR 429: Your IP: 68.154.117.33 has hit the rate limit with Maven Central. Too many requests. Find out more in https://www.sonatype.com/blog/maven-central-and-the-tragedy-of-the-commons.
```

See https://github.com/GoogleCloudPlatform/spring-cloud-gcp/actions/runs/16334302189/job/46143283543?pr=3925.