Cleanup `deduplicate_security_report_ingestion_jobs` and remove old job

What does this MR do and why?

Remove the deduplicate_security_report_ingestion_jobs FF

This gitlab_com_derisk FF was introduced to help us migrate to a new job. We had the FF to allow any queued job using the old code to complete.

The FF has been enabled globally and everything looks good

With the FF removed, the deprecated StoreSecurityReportsWorker class can also have its code removed

To do that, we need to follow the 2-release process. In the first MR, we must:

In the first minor release

• Remove any code that enqueues the jobs.
• Ensure both the frontend and backend code no longer relies on any of the work that used to be done by the worker.
• In the relevant worker classes, replace the contents of the perform method with a no-op, while keeping any arguments in tact.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

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Changelog: fixed
EE: true

related to: #452005 (closed)
resolves #460476 (closed)