Fix filtered key paths

Summary

When fixing gitlab-org/gitlab#484865 (closed), we got rid of the error raised in Version App, but we didn't account for a place where the migrated metrics get filtered out. This made it so that we ignored these metrics for Gitlab instances running versions that have the metrics with the old key_paths.

Testing steps

1. Run the Version app server
2. In Gitlab, update SubmitService STAGING_BASE_URL to Version app url [http://localhost:3000 by default]
3. Trigger a Service Ping in Gitlab console: GitlabServicePingWorker.new.perform('triggered_from_cron' => false)
4. Check the Service Ping in Version App console: UsageData.last.created_at should get set to current time. If it did, make sure that the migrated metrics data is available by checking if UsageData.last.stats['work_item_parent_links_epic_parent'] returns non-nil.
5. In Gitlab app, revert this MR.
6. reload! Gitlab console and trigger another Service Ping: GitlabServicePingWorker.new.perform('triggered_from_cron' => false)
7. Check the Service Ping in Version App console: UsageData.last.created_at should get set to current time & UsageData.last.stats['work_item_parent_links_epic_parent'] should return non-nil

---

• I made sure there are no unverified deployments on staging in #version-gitlab-com Slack channel before merging this MR