Move custom page 404 test to controller specs

So it's similar to the other custom page 404 tests.

Note we're explicitely marking the page as a draft so it's more obvious
what's going on in the test.

spec/controllers/pages_controller_spec.rb

@@ -45,5 +45,13 @@ describe PagesController do
       get :show, params: { id: "nonExistentJavaScript.js" }
       expect(response).to be_not_found
     end
+
+    it "returns a 404 message for draft pages" do
+      create(:site_customization_page, slug: "other-slug", status: "draft")
+
+      get :show, params: { id: "other-slug" }
+
+      expect(response).to be_not_found
+    end
   end
 end

spec/system/site_customization/custom_pages_spec.rb

@@ -2,21 +2,6 @@ require "rails_helper"
 
 describe "Custom Pages" do
   context "New custom page" do
-    context "Draft" do
-      scenario "See page" do
-        custom_page = create(:site_customization_page,
-          slug: "other-slug",
-          title_en: "Custom page",
-          content_en: "Text for new custom page",
-          print_content_flag: false
-        )
-
-        visit custom_page.url
-
-        expect(page.status_code).to eq(404)
-      end
-    end
-
     context "Published" do
       scenario "See page" do
         custom_page = create(:site_customization_page, :published,