Remove Alerts service metric

Alerts service was completely removed:
- https://gitlab.com/gitlab-org/gitlab/-/merge_requests/50913
- https://gitlab.com/gitlab-org/gitlab/-/merge_requests/53534

Alerts service metric was deprecated
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/59899 and we can
safely remove it https://gitlab.com/gitlab-data/analytics/-/issues/8609.

changelogs/unreleased/297029-remove-alerts-service-metric.yml

+---
+title: Remove Alerts service metric
+merge_request: 60149
+author:
+type: removed

config/metrics/counts_all/20210216180456_projects_with_alerts_service_enabled.yml

@@ -6,7 +6,8 @@ product_stage: monitor
 product_group: group::health
 product_category: incident_management
 value_type: number
-status: deprecated
+status: removed
+milestone_removed: '13.12'
 time_frame: all
 data_source: database
 distribution:

doc/development/usage_ping/dictionary.md

@@ -4756,7 +4756,7 @@ Count of projects that have enabled the Alerts service
 
 Group: `group::health`
 
-Status: `deprecated`
+Status: `removed`
 
 Tiers: `free`, `premium`, `ultimate`
 

lib/gitlab/usage_data.rb

@@ -164,7 +164,6 @@ module Gitlab
             projects_with_repositories_enabled: count(ProjectFeature.where('repository_access_level > ?', ProjectFeature::DISABLED)),
             projects_with_tracing_enabled: count(ProjectTracingSetting),
             projects_with_error_tracking_enabled: count(::ErrorTracking::ProjectErrorTrackingSetting.where(enabled: true)),
-            projects_with_alerts_service_enabled: DEPRECATED_VALUE,
             projects_with_alerts_created: distinct_count(::AlertManagement::Alert, :project_id),
             projects_with_enabled_alert_integrations: distinct_count(::AlertManagement::HttpIntegration.active, :project_id),
             projects_with_prometheus_alerts: distinct_count(PrometheusAlert, :project_id),

spec/lib/gitlab/usage_data_spec.rb

@@ -571,7 +571,6 @@ RSpec.describe Gitlab::UsageData, :aggregate_failures do
       expect(count_data[:projects_with_repositories_enabled]).to eq(3)
       expect(count_data[:projects_with_error_tracking_enabled]).to eq(1)
       expect(count_data[:projects_with_tracing_enabled]).to eq(1)
-      expect(count_data[:projects_with_alerts_service_enabled]).to eq(Gitlab::UsageData::DEPRECATED_VALUE)
       expect(count_data[:projects_with_enabled_alert_integrations]).to eq(1)
       expect(count_data[:projects_with_prometheus_alerts]).to eq(2)
       expect(count_data[:projects_with_terraform_reports]).to eq(2)

spec/support/helpers/usage_data_helpers.rb

@@ -98,7 +98,6 @@ module UsageDataHelpers
       projects_prometheus_active
       projects_with_repositories_enabled
       projects_with_error_tracking_enabled
-      projects_with_alerts_service_enabled
       projects_with_enabled_alert_integrations
       projects_with_prometheus_alerts
       projects_with_tracing_enabled