Remove graphql_pipeline_analytics feature flag

What does this MR do?

This removes the graphql_pipeline_analytics that was created in !48267 (merged), leaving only the GraphQL implementation for the analytics page

#290153 (closed)

Screenshots (strongly suggested)

N/A

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