ATO-2539: stop publishing old token signing key in integration

[Louisasa]

Wider context of change

As part of the key rotation we need to stop publishing the old key. This stops publishing it in integration.

What’s changed

Turns on feature flag.

Checklist

• Lambdas have correct permissions for the resources they're accessing. N/A
• Impact on orch and auth mutual dependencies has been checked. N/A
• Changes have been made to contract tests or not required. N/A
• Changes have been made to the simulator or not required. N/A
• Changes have been made to stubs or not required. N/A
• Successfully deployed to authdev or not required. N/A
• Successfully run Authentication acceptance tests against sandpit or not required. N/A
• Added new endpoints to local running (LocalOrchestrationApi.java) or not required. N/A

[github-actions]

Java Tests Skipped

No Java files were changed in this pull request. Java tests will be skipped¹.

Any Java files that are changed in a subsequent commit will trigger the Java tests.

Footnotes

1. These tests will still show as passing in the PR status check, but will not actually have run. ↩