Update policies_helper_spec variables to let_it_be

- this makes the test performance better by not creating a
  new variable every test

ee/spec/helpers/projects/security/policies_helper_spec.rb

@@ -3,11 +3,11 @@
 require 'spec_helper'
 RSpec.describe Projects::Security::PoliciesHelper do
-  let(:project) { create(:project, :repository, :public) }
+  let_it_be_with_reload(:project) { create(:project, :repository, :public) }
   describe '#assigned_policy_project' do
     context 'when a project does have a security policy project' do
-      let(:policy_management_project) { create(:project) }
+      let_it_be(:policy_management_project) { create(:project) }
       subject { helper.assigned_policy_project(project) }
@@ -69,7 +69,8 @@
     end
     context 'when an existing policy is being edited' do
-      let(:environment) { create(:environment, project: project) }
+      let_it_be(:environment) { create(:environment, project: project) }
+
       let(:policy_type) { 'container_policy' }
       let(:policy) do