Service Desk: update ownership of metrics

Acceptance criteria

• All metrics for Service Desk are assigned to grouprespond instead of ~group::certify
  • Service Desk metrics as per the Metrics Dictionary: https://metrics.gitlab.com/keys/service-ping/?q=counts.service_desk_enabled_projects,counts.service_desk_issues,usage_activity_by_stage.plan.service_desk_enabled_projects,usage_activity_by_stage.plan.service_desk_issues,usage_activity_by_stage_monthly.plan.service_desk_enabled_projects,usage_activity_by_stage_monthly.plan.service_desk_issues,settings.service_desk_email_encrypted_secrets_enabled

Example

Taking the counts.service_desk_enabled_projects metric as an example: https://gitlab.com/gitlab-org/gitlab/-/blob/86dc76a9f0bb9e9dfea676a13ed05a4fe1823abe/config/metrics/counts_28d/20210216181148_service_desk_issues.yml

Before

product_section: dev
product_stage: plan
product_group: plan

After

product_section: ops
product_stage: monitor
product_group: respond