TestQueryLatestPolicies400k flaky

## Flaky Test

* **Test Name:** TestQueryLatestPolicies400k
* **Link:** https://github.com/elastic/fleet-server/blob/20990468213ce5517bf986af1f5388a7ec01016e/internal/pkg/dl/policies_integration_test.go#L97
* **Branch:** main

### Stack Trace

https://buildkite.com/elastic/fleet-server/builds/9349#019851e8-3db9-49c9-a5d8-945593eddb80

```

=== RUN TestQueryLatestPolicies400k
--
client.go:81: {"level":"debug","cluster.addr":["localhost:9200"],"cluster.maxConnsPersHost":128,"message":"init es"}
  | engine.go:348: {"level":"info","opts":{"flushInterval":250,"flushThresholdCnt":2048,"flushThresholdSz":1048576,"maxPending":8,"blockQueueSz":32,"apikeyMaxParallel":120,"apikeyMaxReqSize":104857600},"message":"Run bulker with options"}
  | policies_integration_test.go:108:
  | Error Trace: /opt/buildkite-agent/builds/bk-agent-prod-gcp-1753721188864799802/elastic/fleet-server/internal/pkg/dl/policies_integration_test.go:108
  | Error: Condition never satisfied
  | Test: TestQueryLatestPolicies400k
  | Messages: Expected to eventuually have 4 policies found: 0

```