The flaky test fails because the background flushing service unpredictably processes an extra record (4 instead of the expected 3), likely due to a timing race or a data leak from a previous test run.

Fix flaky testFlushOutboxRecordsProtectedByUnleashFlag in JUnit for swatch-metrics-hbi

This test is randomly failing in CI. For ex: https://github.com/RedHatInsights/rhsm-subscriptions/actions/runs/19358882475/job/55385819352?pr=5210

Error:  Failures: 
Error:    HbiEventOutboxServiceTest.testFlushOutboxRecordsProtectedByUnleashFlag:117 expected: <3> but was: <4>

This is causing all the CI to fail. Doing a /retest sometimes fixes it which confirms it's a flaky test.

Acceptance Criteria

• Investigate why this test is flaky and fix it.