[Feature flag] Rollout of: product_analytics_aggregated_metrics

What does this MR do?

Removes product_analytics_aggregated_metrics development feature flag

Parent issue includes all performance analysis

Implements: #267550 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required) https://docs.gitlab.com/ee/development/product_analytics/usage_ping.html#aggregated-metrics
• Code review guidelines
• Merge request performance guidelines
• Style guides