Stop Composer cache file related workers

🌵 What does this MR do and why?

The Composer cache file system is not used, so we are in the process of removing any dead code. #333694 contains details why the system is not used and how we came to that conclusion.

There are two workers related to this code. Removing a worker requires that the worker is no longer being scheduled and any pending jobs are complete before the worker is dropped from the code. This MR:

• No-ops the two workers
• Removes CacheCleanupWorker from the cron
• Removes the only place the CacheUpdateWorker was being called
  • A feature flag was used to safely "turn off" this feature in 14.2. We used it to safely ensure nothing would break if the worker stopped being called. The feature flag has been enabled on GitLab.com (disabling the worker) since 14.2 with no incident. Rollout issue: #338264 (closed)

The workers will be fully removed in a future release. By no-oping them we can now continue to remove the other related code (models/services/etc). See this thread for how this implementation plan was formulated.

📷 Screenshots or screen recordings

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💻 How to set up and validate locally

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📏 MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #333694