Remove purge_stale_security_findings feature flag

Changelog: other
EE: true

config/feature_flags/ops/purge_stale_security_findings.yml

----
-name: purge_stale_security_findings
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/81423
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/356464
-milestone: '14.9'
-type: ops
-group: group::threat insights
-default_enabled: true

ee/app/workers/security/scans/purge_worker.rb

@@ -12,8 +12,6 @@ class PurgeWorker
       idempotent!
 
       def perform
-        return unless Feature.enabled?(:purge_stale_security_findings, type: :ops)
-
         ::Security::PurgeScansService.purge_stale_records
       end
     end

ee/spec/workers/security/scans/purge_worker_spec.rb

@@ -8,28 +8,12 @@
 
     before do
       allow(::Security::PurgeScansService).to receive(:purge_stale_records)
-
-      stub_feature_flags(purge_stale_security_findings: feature_enabled?)
-    end
-
-    context 'when the `purge_stale_security_findings` feature is disabled' do
-      let(:feature_enabled?) { false }
-
-      it 'does not initiate the mark as purged job' do
-        perform
-
-        expect(::Security::PurgeScansService).not_to have_received(:purge_stale_records)
-      end
     end
 
-    context 'when the `purge_stale_security_findings` feature is enabled' do
-      let(:feature_enabled?) { true }
-
-      it 'initiates the mark as purged job' do
-        perform
+    it 'delegates the call to PurgeScansService' do
+      perform
 
-        expect(::Security::PurgeScansService).to have_received(:purge_stale_records)
-      end
+      expect(::Security::PurgeScansService).to have_received(:purge_stale_records)
     end
   end
 end