Remove `gitlab_subscription_future_renewal` feature flag

Changelog: other
EE: true

ee/app/services/gitlab_subscriptions/check_future_renewal_service.rb

@@ -14,7 +14,6 @@ module GitlabSubscriptions
     end
 
     def execute
-      return false unless Feature.enabled?(:gitlab_subscription_future_renewal, default_enabled: :yaml)
       return false unless namespace.gitlab_subscription.present?
 
       future_renewal

ee/config/feature_flags/development/gitlab_subscription_future_renewal.yml

----
-name: gitlab_subscription_future_renewal
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/56235
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/324157
-milestone: '13.11'
-type: development
-group: group::utilization
-default_enabled: false

ee/spec/services/gitlab_subscriptions/check_future_renewal_service_spec.rb

@@ -61,13 +61,5 @@ RSpec.describe GitlabSubscriptions::CheckFutureRenewalService, :use_clean_rails_
 
       it { is_expected.to be false }
     end
-
-    context 'when the `gitlab_subscription_future_renewal` feature flag is disabled' do
-      before do
-        stub_feature_flags(gitlab_subscription_future_renewal: false)
-      end
-
-      it { is_expected.to be false }
-    end
   end
 end