Did you change the policy being used or make any changes to the default policy?
Data streams from integrations will use the default logs lifecycle policy, which never deletes anything, it only rollover data.
If you want to delete a old backing index you can just select it in Kibana and delete it.
Or run
DELETE /.ds-logs-elastic_agent-default-2025.01.06-000004
This will delete the entire index.