Remove Security Dashboard feature flag

This removes the group_overview_security_dashboard feature flag

changelogs/unreleased/rf-remove-group-overview-security-dashboard-feature-flag.yml

+---
+title: Remove Security Dashboard feature flag
+merge_request: 31820
+author:
+type: other

lib/gitlab/usage_data.rb

@@ -100,9 +100,7 @@ module Gitlab
           .merge(services_usage)
           .merge(approximate_counts)
         }.tap do |data|
-          if Feature.enabled?(:group_overview_security_dashboard)
-            data[:counts][:user_preferences] = user_preferences_usage
-          end
+          data[:counts][:user_preferences] = user_preferences_usage
         end
       end
       # rubocop: enable CodeReuse/ActiveRecord

spec/lib/gitlab/usage_data_spec.rb

@@ -154,11 +154,6 @@ describe Gitlab::UsageData do
       expect(expected_keys - count_data.keys).to be_empty
     end
 
-    it 'does not gather user preferences usage data when the feature is disabled' do
-      stub_feature_flags(group_overview_security_dashboard: false)
-      expect(subject[:counts].keys).not_to include(:user_preferences)
-    end
-
     it 'gathers projects data correctly' do
       count_data = subject[:counts]