Flake in `google-cloud-auth` integration tests

[coryan]

This build failed:

https://github.com/googleapis/google-cloud-rust/pull/1985/checks?check_run_id=41554609466

the error shows it was a flake:

---- driver::run_api_key stdout ----
12:46:48 | Error: Error { kind: Rpc, source: ServiceError { status: Status { code: 500, message: "Internal error encountered.", status: Some("INTERNAL"), details: [] }, http_status_code: Some(500), headers: Some({"transfer-encoding": "chunked", "content-type": "application/json; charset=UTF-8", "x-content-type-options": "nosniff", "x-frame-options": "SAMEORIGIN", "accept-ranges": "none", "date": "Fri, 02 May 2025 16:46:48 GMT", "x-xss-protection": "0", "server": "scaffolding on HTTPServer2", "vary": "Origin,Accept-Encoding"}) } }
12:46:48 |  
12:46:48 |  

Looks like we need a retry policy in these tests.

[coryan]

Repeated 5 minutes later...

[coryan]

https://github.com/googleapis/google-cloud-rust/pull/1988/checks?check_run_id=41556322954

[dbolduc]

drats

https://github.com/googleapis/google-cloud-rust/pull/2545/checks?check_run_id=44947823661

[coryan]

No repeats in over 90d, closing.