Remove pages_serve_with_zip_file_protocol feature flag

It was enabled by default in 13.11, so we can remove int 13.12

app/models/pages/lookup_path.rb

@@ -50,8 +50,6 @@ module Pages
     def zip_source
       return unless deployment&.file
 
-      return if deployment.file.file_storage? && !Feature.enabled?(:pages_serve_with_zip_file_protocol, project, default_enabled: :yaml)
-
       global_id = ::Gitlab::GlobalId.build(deployment, id: deployment.id).to_s
 
       {

changelogs/unreleased/321677-enable-and-remove-pages_serve_with_zip_file_protocol-feature-flag.yml

+---
+title: Remove pages_serve_with_zip_file_protocol feature flag
+merge_request: 59908
+author:
+type: added

config/feature_flags/development/pages_serve_with_zip_file_protocol.yml

----
-name: pages_serve_with_zip_file_protocol
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/46320
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/321677
-milestone: '13.6'
-type: development
-group: group::release
-default_enabled: true

spec/models/pages/lookup_path_spec.rb

@@ -47,15 +47,11 @@ RSpec.describe Pages::LookupPath do
   describe '#source' do
     let(:source) { lookup_path.source }
 
-    shared_examples 'uses disk storage' do
-      it 'uses disk storage', :aggregate_failures do
-        expect(source[:type]).to eq('file')
-        expect(source[:path]).to eq(project.full_path + "/public/")
-      end
+    it 'uses disk storage', :aggregate_failures do
+      expect(source[:type]).to eq('file')
+      expect(source[:path]).to eq(project.full_path + "/public/")
     end
 
-    include_examples 'uses disk storage'
-
     it 'return nil when legacy storage is disabled and there is no deployment' do
       stub_feature_flags(pages_serve_from_legacy_storage: false)
       expect(Gitlab::ErrorTracking).to receive(:track_exception)
@@ -107,14 +103,6 @@ RSpec.describe Pages::LookupPath do
             )
           end
         end
-
-        context 'when pages_serve_with_zip_file_protocol feature flag is disabled' do
-          before do
-            stub_feature_flags(pages_serve_with_zip_file_protocol: false)
-          end
-
-          include_examples 'uses disk storage'
-        end
       end
 
       context 'when deployment were created during migration' do