Move `NotificationsController#index` test into their own `describe` block

spec/controllers/notifications_controller_spec.rb

@@ -3,6 +3,7 @@
 require "rails_helper"
 
 describe NotificationsController do
+  describe "#index" do
     subject { get :index, params: { type: :new } }
 
     let(:user) { FactoryBot.create(:user) }
@@ -39,3 +40,4 @@ describe NotificationsController do
       end
     end
   end
+end