Remove feature flag for packages finder refactor

What does this MR do and why?

Refactor packages finder to use package class (!202400 - merged) implemented the refactoring for packages finder with the feature flag.

The feature flag was globally enabled on gitlab.com on 2025-09-01 link.

This MR removes the feature flag for packages finder refactoring.

References

Foundation: Prepare application code to read fr... (#548761 - closed)

Screenshots or screen recordings

No.

How to set up and validate locally

The detailed instruction of how to verify the changes locally is provided here. The first step of enabling feature flag should be skipped.

MR acceptance checklist

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

Related to #548761 (closed)