Job Generator: Remove obsolete configuration

The [introduction][] of `config/initializers/active_job.rb` was rendered
obsolete by [rails/rails#43390][].

Additionally, the following Rails 7 defaults match the [existing
configuration][], so there is no need to redeclare them.

```ruby
Rails.application.config.action_mailer.deliver_later_queue_name
=> nil

Rails.application.config.action_mailbox.queues.routing
=> nil

Rails.application.config.active_storage.queues.analysis
=> nil

Rails.application.config.active_storage.queues.purge
=> nil

Rails.application.config.active_storage.queues.mirror
=> nil
```

This is relevant because the next release of Suspenders will only
support `rails >= 7.0`.

[introduction]: 38b530c
[rails/rails#43390]: rails/rails#43390
[existing configuration]: https://github.com/thoughtbot/suspenders/blob/bd40e33a585891afba380a7884284f5accc003cf/lib/suspenders/generators/jobs_generator.rb#L19-L23

lib/generators/suspenders/jobs_generator.rb

@@ -1,7 +1,6 @@
 module Suspenders
   module Generators
     class JobsGenerator < Rails::Generators::Base
-      source_root File.expand_path("../../templates/active_job", __FILE__)
       desc <<~MARKDOWN
         Installs Sidekiq for background job processing.
       MARKDOWN
@@ -11,10 +10,6 @@ def add_sidekiq_gem
         Bundler.with_unbundled_env { run "bundle install" }
       end
 
-      def initialize_active_job
-        copy_file "active_job.rb", "config/initializers/active_job.rb"
-      end
-
       def configure_active_job
         environment "config.active_job.queue_adapter = :sidekiq"
         environment "config.action_mailer.deliver_later_queue_name = nil"

test/generators/suspenders/jobs_generator_test.rb

@@ -29,26 +29,11 @@ class JobsGeneratorTest < Rails::Generators::TestCase
         assert_match(/bundle install/, output)
       end
 
-      test "configures ActiveJob logging" do
-        expected_configuration = file_fixture("active_job.rb").read
-
-        run_generator
-
-        assert_file app_root("config/initializers/active_job.rb") do |file|
-          assert_equal(expected_configuration, file)
-        end
-      end
-
       test "adds ActiveJob configuration to the application file" do
         run_generator
 
         assert_file app_root("config/application.rb") do |file|
           assert_match(/config.active_job.queue_adapter = :sidekiq/, file)
-          assert_match(/config.action_mailer.deliver_later_queue_name = nil/, file)
-          assert_match(/config.action_mailbox.queues.routing = nil/, file)
-          assert_match(/config.active_storage.queues.analysis = nil/, file)
-          assert_match(/config.active_storage.queues.purge = nil/, file)
-          assert_match(/config.active_storage.queues.mirror = nil/, file)
         end
       end