Remove usage_data_i_source_code_code_intelligence flag

changelogs/unreleased/kerrizor-remove-oprhaned-feature-flag-yml.yml

+---
+title: Remove usage_data_i_source_code_code_intelligence flag
+merge_request: 51765
+author:
+type: other

config/feature_flags/development/usage_data_i_source_code_code_intelligence.yml

----
-name: usage_data_i_source_code_code_intelligence
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/41881
-rollout_issue_url: 
-milestone: '13.4'
-type: development
-group: group::code review
-default_enabled: true

lib/gitlab/usage_data_counters/known_events/common.yml

@@ -165,7 +165,6 @@
   redis_slot: source_code
   category: source_code
   aggregation: daily
-  feature_flag: usage_data_i_source_code_code_intelligence
 # Incident management
 - name: incident_management_alert_status_changed
   redis_slot: incident_management