v2/internal/proxy: TestClientLimitsMaxConnections failed

[flaky-bot]

Note: #2228 was also for this test, but it was closed more than 10 days ago. So, I didn't mark it flaky.

---

commit: 0a98362
buildURL: https://github.com/GoogleCloudPlatform/cloud-sql-proxy/actions/runs/22159849347
status: failed

[flaky-bot]

Looks like this issue is flaky. 😟

I'm going to leave this open and stop commenting.

A human should fix and close this.

---

When run at the same commit (0a98362), this test passed in one build (https://github.com/GoogleCloudPlatform/cloud-sql-proxy/actions/runs/22159849347) and failed in another build (https://github.com/GoogleCloudPlatform/cloud-sql-proxy/actions/runs/22159849347).