Remove feature flag for banzai reference filter optimization

What does this MR do?

As part of Rollout update nodes optimization feature for banzai reference filter, it removes feature flag :update_nodes_for_banzai_reference_filter

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

Related to #230689 (closed)