Remove pages_internal_api feature flag

This API is used only internally, and we don't use this
feature flag inside pages daemon itself

lib/api/internal/pages.rb

@@ -5,7 +5,6 @@ module API
   module Internal
     class Pages < Grape::API
       before do
-        not_found! unless Feature.enabled?(:pages_internal_api)
         authenticate_gitlab_pages_request!
       end
 

spec/requests/api/internal/pages_spec.rb

@@ -14,19 +14,6 @@ describe API::Internal::Pages do
       get api("/internal/pages"), headers: headers, params: { host: host }
     end
 
-    context 'feature flag disabled' do
-      before do
-        stub_feature_flags(pages_internal_api: false)
-      end
-
-      it 'responds with 404 Not Found' do
-        query_host('pages.gitlab.io')
-
-        expect(response).to have_gitlab_http_status(:not_found)
-      end
-    end
-
-    context 'feature flag enabled' do
     context 'not authenticated' do
       it 'responds with 401 Unauthorized' do
         query_host('pages.gitlab.io')
@@ -253,5 +240,4 @@ describe API::Internal::Pages do
       end
     end
   end
-  end
 end