Change failure rate should not include duplicate incidents

Summary

Change failure rate is calculated by number of incidents over number of deployments.

Steps to reproduce

1. Deploy to prod
2. Create incident 1
3. Create incident 2
4. Check CI/CD dashboard and the change failure rate is 200%
5. Make incident 2 a duplicate of incident 1 (using /duplicate)
6. Check CI/CD dashboard and the change failure rate is still 200%

What is the current bug behavior?

Change failure rate is 200%

What is the expected correct behavior?

Change failure rate is 100%

Output of checks

This bug happens on GitLab.com