fix(dashboard): Correct the metric name
We renamed the SLI, but did not update this dashboard. This fixes that.
For gitlab-com/gl-infra/scalability#2028 (closed)
Snapshot: https://dashboards.gitlab.net/dashboard/snapshot/HSM9iW2cnnom5LEmtukWC5N11A3bJSsL?orgId=1
Edited by Bob Van Landuyt