Move merge_requests_users under counts section

This is so it can show up on versions.gitlab.com. It also makes
sense to be added under that section since it's a count.

doc/development/telemetry/usage_ping.md

@@ -429,6 +429,7 @@ On GitLab.com, we have DangerBot setup to monitor Telemetry related files and Da
 | `projects_jira_dvcs_server_active`                      | `counts`                           |             |                |                                                   |
 | `labels`                                                | `counts`                           |             |                |                                                   |
 | `merge_requests`                                        | `counts`                           |             |                |                                                   |
+| `merge_requests_users`                                  | `counts`                           |             |                |                                                   |
 | `notes`                                                 | `counts`                           |             |                |                                                   |
 | `wiki_pages_create`                                     | `counts`                           |             |                |                                                   |
 | `wiki_pages_update`                                     | `counts`                           |             |                |                                                   |

lib/gitlab/usage_data.rb

@@ -37,7 +37,6 @@ def uncached_data
           .merge(object_store_usage_data)
           .merge(topology_usage_data)
           .merge(recording_ce_finish_data)
-          .merge(merge_requests_usage_data(default_time_period))
       end
 
       def to_json(force_refresh: false)
@@ -162,7 +161,8 @@ def system_usage_data
             usage_counters,
             user_preferences_usage,
             ingress_modsecurity_usage,
-            container_expiration_policies_usage
+            container_expiration_policies_usage,
+            merge_requests_usage(default_time_period)
           )
         }
       end
@@ -400,7 +400,7 @@ def user_preferences_usage
       end
 
       # rubocop: disable CodeReuse/ActiveRecord
-      def merge_requests_usage_data(time_period)
+      def merge_requests_usage(time_period)
         query =
           Event
             .where(target_type: Event::TARGET_TYPES[:merge_request].to_s)

spec/lib/gitlab/usage_data_spec.rb

@@ -580,7 +580,7 @@ def stub_runtime(runtime)
     end
   end
 
-  describe '#merge_requests_usage_data' do
+  describe '#merge_requests_usage' do
     let(:time_period) { { created_at: 2.days.ago..Time.current } }
     let(:merge_request) { create(:merge_request) }
     let(:other_user) { create(:user) }
@@ -597,7 +597,7 @@ def stub_runtime(runtime)
     end
 
     it 'returns the distinct count of users using merge requests (via events table) within the specified time period' do
-      expect(described_class.merge_requests_usage_data(time_period)).to eq(
+      expect(described_class.merge_requests_usage(time_period)).to eq(
         merge_requests_users: 2
       )
     end

spec/support/helpers/usage_data_helpers.rb

@@ -78,6 +78,7 @@ module UsageDataHelpers
       labels
       lfs_objects
       merge_requests
+      merge_requests_users
       milestone_lists
       milestones
       notes