Remove unused composer rake task

🎋 Context

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

🔦 What does this MR do and why?

This MR removes an irrelevant rake task related to the composer cache file system.

This will allow us to further remove the related Composer::Cache model code in future MRs.

📽 Screenshots or screen recordings

N/A

✏ How to set up and validate locally

N/A

☑ 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 (closed)