add missing require to have_enqueued_mail

Author: ignatiusreza

lib/rspec/rails/matchers.rb

@@ -22,4 +22,5 @@ module Matchers
 require 'rspec/rails/matchers/have_http_status'
 if RSpec::Rails::FeatureCheck.has_active_job?
   require 'rspec/rails/matchers/active_job'
+  require 'rspec/rails/matchers/have_enqueued_mail'
 end