Remove the feature flag npm_metadata_cache

What does this MR do and why?

The feature flag npm_metadata_cache was enabled globally on 2023-11-17: link (internal)

This MR removes the feature flag npm_metadata_cache to use npm metadata cache in all cases.

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 #393745 (closed)