Use worker name instead of queue for MailRoom SLIs

For gitlab-com/gl-infra/production#7539 (closed)

In gitlab-org/gitlab!93462 (merged), we change the queue name of EmailReceiverWorker and ServiceDeskReceiverWorker to urgent_other. The prior names were email_receiver and service_desk_receiver. This change was expected long time ago; hence, we converted to filter the workers using worker label, instead of queue label in the Runbooks. Unfortunately, there is still one place where we still use queue as a selector. That place defines the SLIs for mailroom. That leads to incorrect metrics after gitlab-org/gitlab!93462 (merged) reaches production. This MR is to fix the selector.

Before

After

As the SLIs use recording rules, the results won't be reflected on the dashboards instantly. We'll have to wait until the new metrics kick in.

New SLI query after being autogenerated

The metric is identical to the previous version

Source: https://dashboards.gitlab.net/explore?orgId=1&left=%7B%22datasource%22:%22Global%22,%22queries%22:%5B%7B%22refId%22:%22A%22,%22editorMode%22:%22code%22,%22expr%22:%22%20%20%20%20%20%20%20%20sli_aggregations:sidekiq_jobs_completion_seconds_bucket_rate1m%7Ble%3D%5C%22%2BInf%5C%22,worker%3D%5C%22EmailReceiverWorker%5C%22,%20env%3D%5C%22gprd%5C%22%7D%22,%22legendFormat%22:%22__auto%22,%22range%22:true,%22instant%22:true,%22hide%22:false%7D,%7B%22refId%22:%22B%22,%22expr%22:%22%20%20%20%20%20%20%20%20sli_aggregations:sidekiq_jobs_completion_seconds_bucket_rate1m%7Ble%3D%5C%22%2BInf%5C%22,queue%3D%5C%22email_receiver%5C%22,%20env%3D%5C%22gprd%5C%22%7D%22%7D%5D,%22range%22:%7B%22from%22:%22now-7d%22,%22to%22:%22now%22%7D%7D