Fix Service ping failing metrics for create stage (5)

Summary

The following metrics are failing in GitLab.com for devopscreate

• usage_activity_by_stage_monthly.create.merge_requests

Resources

• See Service ping guide for how to optimize queries
• Use Metrics dictionary to find more information about metrics
• Rest of failing metrics (previously encountered) #345248 (closed) #344256 (closed) #349600

• Check the following YAML files and verify the metric is not used in an aggregate:
  config/metrics/aggregates/.yaml
  ee/config/metrics/aggregates/.yaml
  

• Verify the metric is not used to calculate the conversational index. The conversational index is a measure that reports back to self-managed instances to inform administrators of the progress of DevOps adoption for the instance.

• Verify that removing the metric from the Service Ping payload does not cause errors in Version App when the updated payload is collected and processed. Version App collects and persists all Service Ping reports. To verify Service Ping processing in your local development environment, follow this guide. Alternatively, you can modify fixtures used to test the UsageDataController#create endpoint, and assure that test suite does not fail when metric that you wish to remove is not included into test payload.

• Remove data from Redis

• Create an issue in the GitLab Data Team project. Ask for confirmation that the metric is not referred to in any SiSense dashboards and can be safely removed from Service Ping. Use this example issue for guidance.

• After you verify the metric can be safely removed, update the attributes of the metric’s YAML definition:
  Set the status: to removed.
  Set milestone_removed: to the number of the milestone in which the metric was removed.
  

• Do not remove the metric’s YAML definition altogether. Some self-managed instances might not immediately update to the latest version of GitLab, and therefore continue to report the removed metric. The Product Intelligence team requires a record of all removed metrics in order to identify and filter them.

• After you verify the metric can be safely removed, remove the metric’s instrumentation from lib/gitlab/usage_data.rb or ee/lib/ee/gitlab/usage_data.rb.

• Remove any other records related to the metric:
  The feature flag YAML file at config/feature_flags//.yaml.
  The entry in the known events YAML file at lib/gitlab/usage_data_counters/known_events/*.yaml.