Remove `projects_jira_dvcs_cloud_active` metric

With the !134791 (merged) we removed all usages of the Jira DVCS, and with the !134791 (comment 1620156107), we decided to clean up the metrics in a follow-up issue.

The counts.projects_jira_dvcs_cloud_active is no longer needed, since we're dropping cloud support for the Jira DVCS.

We should follow the docs to remove the metric.