Cleanup package metadata feature flags

What does this MR do and why?

Cleanup package_metadata_synchronization and compressed_package_metadata_synchronization since they were rolled out in [Feature flag] Rollout of package_metadata_sync... (#390836 - closed) and [Feature flag] Rollout of `compressed_package_m... (#410230 - closed)

Related issue: #422261 (closed)

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

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.